Now, if you could get the raccoon to chase the cat around... + =
Anyway, yeah...using an outboard mixer is an option IF said mixer can deal with the higher levels coming directly off the synth. I know my (1st version) Mackie 1202 can do that on channels 1-4 with the adjustable trims, but I'd be hesitant to use the two stereo strips at anything other than line-level because the gain structure might get sort of janky and hard to control. However, I've heard from many users that Allen & Heath's ZED series mixers are more than capable of handling synth-level signals...and then some. Their theoretical top-level very much exceeds what would come off of a 'raw' synth module, and then you also get EQ, FX sends and potentially channel inserts provided the levels get stepped down before the insert send. And yeah, using the ER-301 for just noise-type sounds is sort of like using a proverbial sledgehammer to swat a proverbial mosquito; you might be able to build up something space-saving with some 2hp modules + one or two dedicated drum modules like what's in place already.