What would be your angle for the blower filter and access?
Personally, I think you have the right idea, just bolt a 2.5 flanged elbow to the "lid" of the filterbox pointed towards the blower, and use another threaded 2.5 elbow from blower and a rubber fernco to join em, and skip the blower filter, deal with filtration out front, that would make for some easy blower exhaust plumbing for sure, and a decent muffler, then that would allow the HX to only have engine exhaust, it would surely get hotter, but then you need to add a heat management system, not too bad if you ask me, simple. I would wrap that HX as well.