Found a problem with the catch can idea - there's nowhere for me to put it that doesn't form a p-trap with the hose, or have the catch can hanging very low on the car (bottom of catch can around bottom of transaxle ... I'd be worried about some manometer effect I didn't think of and somehow accidentally end up draining the transaxle) or have the hose hitting the exhaust
So i went to the simpler solution - I ran a ~10'' section of -6 hose straight(ish) up from the original vent location then stuck the oem vent into the other end, hose clamped it on and attached it to my roll cage with a rubber insulated mounting clip, pointing vent hole slightly up-ish
this way any fluid slung into it will naturally bleed back down into the transaxle and the only way fluid should come out is if the fluid has to vent from pressure (at least I hope that's the only reason).
Hopefully this solves my issue - I drove the piss out of my 917 for a few miles and when i got back it the area was bone-dry. First time in 2yrs.