I looked over my third run and determined some things that I could cut out, and so no shopping or forging is done at all this time around. I also made sure to use all three save slots in order to be extra picky about the time for each chapter, and for maximizing Marth's level ups. While this made the whole process take a lot longer to complete, it definitely paid off for my in-game time.
Edit: Screenshot added because I can (click for larger version):
Chapter breakdown:
Prologue 1: Make sure Marth gains strength, at the very least. Speed is no doubt helpful, but he needs that point of strength to one round that Axe Fighter in Prologue 2.
Prologue 2: Only move Marth and obtain as many self-defense kills as possible, since they are quicker. Ignore the Archers.
Prologue 3: Only use Marth and Jeigan here, but have Freyr give Marth his Iron Sword and Vulnerary on turn one. Jeigan's purpose for this chapter is merely to soak up some damage and kill the yellow square Mage. Use Vulneraries with Marth as necessary, because hoping for fantastic evade is too absurd to bother with.
Prologue 4: Marth should kill the Hand Axe guy on turn one, and then Jeigan slaughters the Archer on turn two by using the Silver Lance. Marth is to move toward the boss while Jeigan's only remaining purpose is to kill Gordon (easily faster than sacrificing a unit).
If things have been going properly, Marth's Iron Sword should be at 6/40 when approaching the newly opened door. Two of those go to the Archer in front, and the other four obviously go to the two Soldiers standing behind that guy. All so very convenient, don't you think?
Anyway, the rest is simple. Move Marth up and Rapier the boss into a pile of goo. Be ready to skip the scene and the reinforcement appearance soon after emerging from the other end of the Gordon area.
Chapter 1: This one is extremely straightforward. Marth moves above the left tree on turn one, to the middle tree (it should be obvious which one I mean) on turn two, and then make your way to the boss from there. If you get lucky, the Hunter will attack from one space below and to the left of Marth, making the move to the left slightly faster.
For the boss, you have a decision to make: strike first and waste time with the pre-fight dialogue and Enemy Phase heal (all of which can be sped up, but still wastes some frames anyway), or counter critical at some single digit percentage. Keep in mind that you have no save points to make use of to make this manipulation easier.
Chapter 2: Move Jeigan onto the north bridge, so that he can protect your other wimps. This is important, because less characters risks getting slapped with a Gaiden chapter, which is unacceptable in all cases except 24x. Marth moves left and eventually crosses the river manually, getting a ton of self-defense kills. Kill the boss in self-defense as well, and a winner is you.
Chapter 3: Move Rena down, Marth obviously goes left, and leave Julian to rot. Continue to move those two units until Rena is very close to the fort, at which time you should move Jeigan two spaces above that fort. Keep a close eye on the radar on the top screen as turns begin/end, so that you can tell if Jeigan survives or not. If he dies, Rena is obviously going to become toast, which is crippling.
After stopping Marth next to the boss, I'd recommend pressing L and having the nearest unit use the save point at the starting location. Manipulate a low chance critical and win.
Chapter 4: Equip Marth with a Rapier (or do this in Chapter 3, which may be a better idea) and Warp him to the boss. Marth should have a full inventory by this point, so when he counter kills the boss (which is very important), you should send the Rapier into storage. Hope that Marth kills the peons so that the gate is clear, then seize. Send the Knight Killer back when you get the free Silver Sword.
Chapter 5: Marth goes to the boss and you should leave everyone else to rot. I had Marth kill the boss with a Rapier while standing on his left side, but standing below him probably works just as well. Standing on his right side is a bad idea because if Marth takes damage, you'll waste time from the auto-heal. Send the Rapier back if you want to be sure of the usage.
Chapter 6: Warp Marth and counter kill the boss with a Rapier, which will likely require at least one critical hit. Send it back if you wish.
Chapter 7: Only deploy Marth and move toward the right side of the boss when you get the chance. You should probably send the Rapier back.
Chapter 8: Warp Marth and drop the boss in self-defense (as usual).
Chapter 9: Warp Marth and win. You can pretty much use whatever weapon you want, so send back the Door Key that the boss drops.
Chapter 10: Warp Marth and hope the boss dies during the Enemy Phase. Send the Rapier back when he does. Minerva will likely commit suicide, so send her axe back too.
Chapter 11: Warp Marth and win. If you have any trouble here, you're a moron.
Chapter 12: Kill the Warp Thief with a person that has a full inventory, and then have Rena fetch it from storage and use it. Send Marth to the right side of the boss and drop the Priest. Smoke the boss on the next turn, and then seize on turn three. Obviously, he'll need some luck to survive all this.
Chapter 13: Warp Marth to the boss and drop him, since you can't do so in self-defense. If he gains a level from this kill or from killing Astoria, waste a turn and let the level up occur during the Enemy Phase of turn one (from Astoria). Even though it increases your turn count by one, it should be a tiny bit faster overall (especially if it was some sort of super level up).
Chapter 14: Warp Marth and counter kill the boss with a Rapier, then send it back. Hope that Rena dodges the ballista shot during the Enemy Phase, because a single shot will more than likely kill her. Use the unit count and/or radar to determine her status before turn two begins (to save time).
Chapter 15: Warp Marth to the generic "boss" and then drop him, since you can't get a self-defense kill here. Extremely easy chapter.
Chapter 16: Warp Marth to the left side of the boss and Rapier counter kill him (send it back). You'll also need to hope Marth survives, because he'll be enduring some serious abuse. If an enemy clogs the gate before turn two, restart.
Chapter 17: Move Jeigan and Zagaro toward the area where the Warp Thief will escape to. Avoid being in range of the Armor Knights on turn one, and then rush in after that. Warp Marth to the boss one turn before obtaining the new Warp staff. Kill the boss in a counter and then use Jeigan and Zagaro to kill the Warp Thief (send the staff back, if possible) before seizing the throne.
Chapter 18: Warp Marth to the left side of the boss and counter kill him with the Rapier. Definitely send the thing back afterwards, because you don't want to slaughter the whole army in that area with it.
Chapter 19: Warp Marth to Chiki and it's up to you whether to strike first or not. I'd probably do that, since her damage might be a little excessive considering you need Marth to survive several magic attacks and some Heroes.
Chapter 20: This one suffers from the lack of Boots. Drop someone from your group so that Rena can be one space below Marth, Warp Marth to the village, visit it, and then have him run back to the right (using Vulneraries on the way, if need be). Your next goal is to have Rena meet him and then Warp him to Lawrence so that he can recruit him that turn (cannon fodder).
While doing this, move Zagaro or some other high movement unit toward the save point. Save on the turn that you send Marth to Lawrence, in case Camus roasts Marth. Saving obviously wastes time though, so if you feel confident in Marth's survival skills, avoid the save entirely.
Chapter 21: Send Marth to the boss on turn one and repair a Warp staff on turn two. If you are having troubles with that Enemy Phase, you could try repairing first and sending Marth over later. This will cost you a turn though, so keep that in mind.
Chapter 22: Warp Marth to the boss and hope for survival and a clear gate. Seize on turn two.
Chapter 23: Warp Marth to the generic boss and hope things go well (pretty easy, actually). Seize on turn two.
Chapter 24: Same as the plan for Chapter 22.
Chapter 24x: Same as the plan for Chapter 22, but with a throne instead of a gate. One or two of your units might die here, but it doesn't matter (as long as it wasn't Rena or Ellis).
Chapter 25: Drop everybody except Marth, Rena, and Ellis. Give Ellis one of Rena's Warp staves and make sure both of them are in position near Marth. Warp Marth and Nagi to either side of the Mamkute and have Nagi drop him. Use Marth to critical Medeus for the kill. Keep in mind that you need 23 strength to kill Medeus in a single shot (with the fake Falchion) and that you will save a good chunk of time by making it a one shot kill. No save points are available to you, so I highly recommend saving after the preparations.
Well, there you have it. That is how I did this 16.57 run, and that is how I think any run of this game should go. Good luck to anybody who wants to try this.
