Ironically, with just a little bit of tweaking, you've effectively reinvented 4e but with 20 levels instead of 30.
That is, in 4e, at even levels you'd get a feat plus either utility powers or increased stats (and, regardless, increase the half-level bonus). At odd levels, you'd get some kind of active combat action. A few extras here and there, mostly at 1st, 11th, and 21st, aka the starting levels of each tier. (The only exception I can see was at 10th level, where you got a bonus utility power.
In other words, more or less, your combat capabilities would always remain more or less the same on even levels, so you'd have time to adjust to what you'd chosen to add (or replace) at the previous odd level. You'd just get better at doing those things.