Huh. I was going to use Chi Focus in one of my games, in approximately the way that Psionic Focus is used in the psionic SRD. I've actually got a coupld of feat trees built around it. DevianID's Focus and Chi ideas sound reasonable to me, but they do sound a bit like they'd pump up the power level of a game - which of course may be the whole point. Making super-human heroes calls for a few mods.
I, too, really like the Size Modifier idea. Sadly, I still don't have the pdf (but it looks like there's money on the horizon, so it may be soon!), so I have no idea what the page 84 modifiers look like. Ah well. For the time being i'll just use the same modifiers as attack/defense, but inversed.
The Shadow's suggestion regarding shapeshifting/Wild Shape sounds appropriate for most campaigns, but I can easily envision one where the looser one-power to take many shapes would make sense - for instance, a game where the magic is more of a fairy-tale style than heroic or romantic fantasy. (Enchanted Forest Chronicles? Oooh!)
Here's one I'm kicking around, though: Levitation. Using Move Object on yourself seems a bit off, since even fatiguing yourself would require some hefty rolling, at least for low levels. So here's my proposal:
Levitation [Shaping, Fatiguing]
You gain a fly speed equal to your move speed so long as you maintain total concentration. If you are carrying any equipment (besides the clothes you are wearing), or attempting to carry any creature with you, you must make a check against that total weight [using the Move Object chart]. By risking fatigue, you can carry ten times the listed weight [as per Move Object]. Note that carrying capacity and load rules still apply when levitating, so your speed may be reduced just as if you were walking.
Time: Levitation is a standard action. It requires total concentration to maintain.
Which leads inevitably to a new feat:
Prerequisite: Levitation (5 ranks)
You find it easier to levitate your own body. You can levitate as a move action, and only require concentration (instead of total concentration) to maintain the power.
Any suggestions on this idea? The intent is to allow characters who can really travel by floating, like the Strangers in the movie Dark City. I know in a lot of games being able to float is an immense advantage, so I'm wondering if the movement rate should be cut in half, with the option to set it back to full speed by risking fatigue or by taking an appropriate feat. (I just want to find the balance to make it worthwhile without making it too good to be true).
EDIT: I had an additional idea. Without attacks of opportunity and tactical movement and all that, a creature's size is slightly less important, tactically, than in standard d20 rules. I appreciate the simplicity of that, but there's a few monsters that always employed particular tactics in my games, based on their size and reach. So I've added a quality called "Bulk." This dictates the fighting space the creature prefers, and any tactical advantages it gains based on its size. [it will probably be worth noting that i never quite bothered to adapt 3.5 size rules.]
For example, a large monster such as a Yeti might have the note:
Bulk: A yeti prefers to fight in a 10'x10' space; if forced to fight in a smaller area, it is unable to use its Dodge defense but can attack foes up to 10 ft away (even reaching over the heads of other combatants). As a move action, the yeti can block a 15 ft width.
No kitten is going to tell me what to do. I'll fall off this branch to my death if I feel like it!