You might want to consider changing the formula for cooldown reduction.
Right now max reduction is capped at 50%, a formula without a cap would be (1/1+x).
This way you would reach half cooldown with 100% reduction, a third with 200% and so on.
But you'd never reach 0.
It's effectively a passive production buff that scales with how much +XP research you have, what's not to like? :)