Hm, just to chime in on the seeds/augment idea, my personal opinion is that it would a great system for a PBP, where there's more time available to consider your options, but it's too complicated for tabletop play. I prefer a psionics-esque system of base spell, each one has one or two specific augments that are relatively simple and scale off to infinity. The main reason is that I LIKE the ability for low-level choices to remain valid at high levels, and I like the ability to tailor individual actions to situations. I think a system like this makes it easier to do that quickly, because even if you need to know more information overall, it's easier to work with it because there are fewer combinations possible and you need to know less for each individual action.
As far as conditions go, if we're still talking about that here, I want to suggest that immunities are a bad idea, for every case but one: if a target simply lacks the thing that is affected, an immunity is valid. A mindless undead should be immune to charm, most oozes should be immune to tripping, or most plants should be immune to traditional blinding. I mean, dividing it up based on means of attack is just fine, it can work either way (and there's a definite appeal to doing it that way), I just mean that, generally, "immunity" should be handled by large bonuses against such effects. So a sufficiently kickass enchanter can still charm that vampire. It's just really, really hard. Part of this involves making it so that spellcasters don't have access to effects that simply win, which would render bonuses a moot point. Add saves for partial effect to everything possible, and if necessary give "immune" creatures an evasion-like ability that lets them ignore the "partial" on a successful save, maybe.