As per popular demand, Lock and Reroll mechanic has been added when selecting the drone upgrade. If you find a perk that you like, but there is also another one that you would like to select, you can lock one of those so it appear in the next upgrade cycle.
Also, if you don't like any of the upgrades, you can reroll.
At the moment, 3 locks and 3 rerolls are available on start of the game. Every five levels you get +1 reroll and after every boss death you get +1 lock.