AP boosters

You could get them for doing a wide range of actions, ie.:

creating a company, battle achievements, login streak, work streak and so on.

It should be a continuous flow, this way players could gather them and do tremendous damage in battles, making them much more unpredictable and risky.
The flow could be adjusted by you to a certain level so it wouldn't get out of control.

This would also be a great way to give more meaning and weight to many achievements we already have.

Oh, and by boosters I mean AP packs basically, filling up your AP bar to a certain level, either a percentage or a flat value.
Or, which is even better actually, more "gameish" imo, to boost the rate of filling up dramatically for a certain amount of time, or until the packs value depleted (ie it would fill up the bar 5 times)

A small meter like this or anything similar could be displayed, representing the speed of the AP recharge when a booster is active for example, or even a light or something indicating that it's active.