I've been playing around with this one for a few weeks now. It's actually one of my favorite FF games (I know, I'm in the minority...) and it's the only one from the pre-Sony generation that doesn't have a TAS run on the site yet.
As pointed out earlier in the thread, it's possible to avoid all random battles in this game. There are a few ways of doing this (in order, from fastest to slowest):
-On the overworld, you can save and power cycle, which resets the step counter. The disadvantage of this is that the first battle on the list is only a few steps from the start. By resetting 5 frames after a power cycle, you can skip the 800+ frame intro and go right to the loading screen.
-Also on the overworld, on the step before a battle, you can save, exit the menu, take a step, and reset, which skips the battle but doesn't reset the step counter. This is slower than a power-cycle, because you have to exit the menu and take a step before resetting.
-Using potions advances the step counter for some reason, and can be used to skip battles in dungeons. This is faster than entering a fight and running, but you also have to factor in the time spent getting potions.
-You can also advance the step counter by using healing spells, but spells only advance the step counter when they actually heal damage. Thus, you have to find a way to damage your party members in order to use this technique. Since I'm not planning on fighting any random battles if I can help it, this isn't going to be particularly useful.
Concerning the glitches TaoTao pointed out, the spellbook equip glitch can save a lot of time in battles, but at this point, I don't think any of the memory corruption effects can save time. The problem is the fact that you need two characters using spellbooks to alter the memory (one to change the value you want, and another to change another value in order to correct the checksum) and this can take a lot of time in battle. It might save time going from Altea to Semmite Falls and Salamand, but given the time it takes to execute the glitch, I can't imagine it would be substantial. As for the 45 floor glitch, all I can do with it is crash the game at this point. I'm not sure if there's anything else you can do with it...
Sadly, this game does not take kindly to sequence breaks. I've tried going to Dist early by stealing a boat, but it doesn't accomplish anything or move the story along from that point. Same thing with the Tropical Island. I'm going to try skipping the Pirate battle and Leviathan, but I can't say that I'm particularly optimistic. Right now, it's looking like the entire game will have to be played.
Here's what the route for my test run looks like right now:
Lose the battle against the Black Knights, buy 8 potions in Altea, walk to Fynn.
Get the Ring from Scott and the three potions in his room and walk back to Altea.
Get Mingwu and the Canoe, sell the Ether he's carrying and buy a Fire Spellbook, take the boat from Palm to Poft, and the Airship from Poft to Semmite Falls (this MIGHT be a place to use the spellbook glitch to warp, but I doubt it would save time).
Go through Semmite Falls, defeat the Sergeant in one turn with the Fire Spellbook, get the Mithril, and use Mingwu's Teleport spell to escape.
Walk/sail/canoe to Fynn and fight 5 Captains for Fire Bows (this might be able to be done later... I'll have to investigate that). Canoe back to Altea and give the Mithril to the guy in the Weapon Shop, then get my next mission from Hilda.
Walk/sail back to Poft and take the airship to Bafsk. Buy 8* potions in the item shop, then enter the sewers, talk to the Black Knight, get the pass, and warp out.
Walk/sail back to Altair via Poft, making sure to unequip Mingwu's Fire Spellbook during the last menu screen.
Talk to Hilda, lose Mingwu, learn about the Goddess Bell, and buy 17* potions at the item shop.
Walk/sail to Salamand via Poft, talk to Yozef, get him on the team, and buy a Teleport Spellbook at the magic shop. Walk to Semmite Falls again, teach Frionel the Teleport spell in the menu screen while skipping a battle, get the ice sled, and teleport out.
Walk/canoe up to the snowfields and sled to the Snow Cave. MAYBE get the South Wind item (for the Pirate battle, if it's faster than getting the Mage Staff later). Give Yozef the Fire Spellbook and beat the Adamantoise, get the Goddess Bell, beat Borghen, and get Yozef buried under rocks. Walk/canoe to Poft and take the airship to Kashuon.
Enter Kashuon, get Gordon in the party, give him the Fire Spellbook, beat the Red Soul, get Egil's Torch, and warp out. Re-enter Kashuon, get the Sunflame, and warp out again. Walk south to the Chocobo forest, wrangle a Chocobo, and trot south to the Dreadnought.
Get stuck at the Dreadnought because of the stupid inventory limit and the stupidly large number of battles, especially when combined with Kashuon.
...And that's where my test run is stuck I'm trying to figure out which way would be faster:
-Riding the Chocobo back to Bafsk instead of going straight to the Dreadnought, stocking up on potions, walking back to the Chocobo Forest, and riding to the Dreadnought.
or...
-Saying "screw it!" and jumping headfirst into the Dreadnought, running from battles after the potions run dry.
There's also a third option, but it might screw things up down the line:
-Riding the Chocobo back to Poft, buying potions, stealing the ship, and sailing to the Dreadnought.
The downside is that you can't re-enter the ship after you've stolen it without using the Spellbook glitch to modify the save data, and that involves buying the Esuna spellbook in Bafsk and successfully changing the ship value and checksum (something which I haven't been successful at yet).
*It would be faster to buy 25 potions at Bafsk instead of 8 at Bafsk and 17 at Altea, except that buying 25 potions somehow changes the NPC movements in the town. This is something else to explore once I figure out the larger issues of this run...