The boots in question aren't those ones irdeggman: they aren't the ones with 5 charges that allow you to move 20, 40, or 60 feet (these are a standard action to activate). They are the ones that allow you to teleport 20 ft. 5/day (as a move action).
Regarding the pit trap, you get a reflex save to avoid falling into a pit trap. You don't automatically fall into one every time you step onto one. I can see what you are saying, and I like the idea of how you run time in combat, but it doesn't really make any sense to me.
I understand everyone goes in the same 6 seconds, But it's not really how combat in D&D works out. You'd really have to make everyone take their turns at the same time for it to work out that way. Everyone would have to move their minis (including all the monsters and NPCs) at the exact same time, probably stopping every 5 feet to adjust their angle, which would horribly slow down gameplay. I don't even wanna think about standard actions at the same time.
Let's say, outside of combat, a character in the front of marching order randomly takes off ahead of his group, using a move action to move 20 feet down a hallway, and 10 feet around a corner, activating a pit trap. From how I understand what you said, by your rules everyone would get a chance to run up to him and try and catch him before he falls, or if not, he would still get a chance next round (?) to cast feather fall? But if he ran around the same corner, and nothing happened, no one would care as much, and probably wouldn't race ahead with him, therefore changing their actions. You would have to keep the knowledge of what happened to the character around the corner secret from the rest of the group for them to not meta game.
Now, lets say the first person in marching order doesn't take off, and is 5 feet away from the person behind him in line. They are marching along, and he steps on a pit trap. I'd give him a reflex save, and the person behind him a dexterity check to try and catch him.
About saying my player can't "move" because he weighs too much doesn't apply to this situation; he is falling, not moving under his own ability.
Anyways, I feel bad about arguing with you; your way probably makes more sense than normal, and I'm just not seeing it. Thanks for all the help you've given though, I appreciate it.
Elethiomel: I didn't really know which way to go, because Enlarge Person states "All equipment worn or carried by a creature is similarly enlarged by the spell". I think I will just double it like you say, but it doesn't really make much sense. Oh well.