It sounds like you've got a fairly good plan as is. My biggest concern would be balancing it among the classes.
As to doing that... I think my best idea would be to list out everything that is going to require Ki points (in other words, I guess most of the resources that a class has).
Then, tally up how much each class gets in a given day to find what seems a good baseline amount of ki to be gained from leveling. This way, leveling in one class doesn't give far more ki points than leveling in other class, which could then be used for the one that gave less. If they are all going to use them, they should all advance about the same amount, I think.
After you've got a baseline for advancement, adjust how much ki the abilities cost accordingly, so that they still have approximately the same progression the classes would under normal circumstances.
That's just pretty much off the top of my head though, and I haven't looked at any numbers to see how it might go. Possibly a start though, at least.
If spell casters are garnering GOBS of ki to power all of their spells, then perhaps one should consider that all ki users gain ki pools based on the gains of full casters.
I'd probably use the sorcerer's spells/day to generate the base ki pool based on the 1/2 ki per spell level, add in the casting ability score with attendant increases in ki pool and basically you have an all-ki setting. 1-6 casters [bards, summoners] get full pools too, although most class abilities consume ki - performance and summons for example. Change the eidolon to cost ki but not interfere with summons, be summonable as a move or swift action, etc. Certain class abilities simply shouldn't cost anything - versatile performance, jack of all trades, etc.
Rage would burn ki like candy - 1 ki per round + a ki cost per rage power used + increasing costs based on stuff like having greater rage, the various feats that permit burning extra rage to get larger or still take full rounds while at 0 or negative hit points and so on. Or just throw such things into Rage as bonuses, toss out the 1/rage stuff and the rage powers that provide immunities simply add icing onto the cake of Rage. [In trade, they don't get to smash stuff or make floors into gravel like other Ragers do.]
1-4 casters get half ki pools - paladins and rangers - as they have largely passive abilities with a small number of goodies that would burn ki. Smite Evil is the big one, especially if detect evil has a ki cost the "evil radar syndrome" will stop PDQ. Smite Evil burns ki per round per declared target, or maybe per minute, depending on how the playtests go.
Just a few dribblings for you.