Hearthpwn

No, without the Battlecry, Dr. Boom, Mad Genius would be severely underpowered.  It'd also remove the core fantasy of Dr. Boom with his army of mechs.

That said, I don't think a redesign to weaken the battlecry would be inappropriate.  Something like "For the rest of the game, your mechs which cost 3 or less gain rush" would be fine with me.  Or "For the rest of the game, when you summon a mech with 3 or less power, give it rush."  That'd be reminiscent of the pre-nerf Warsong Commander.  Obviously, the "X or less" could be tweaked, depending on need.

Keeps the same theme, but is significantly less powerful.  Not every mech would gain rush, but there'd be cool work arounds with playing a smaller mech to gain rush, then magnetizing something bigger onto it.

I'd also change Delivery Drone to give a random mech, since that'd just be more fun.  Less favoring powerful class mechs, and there'd be wild moments getting mechs from other classes.