Okay, I've experimented a bit with OpenAL EFX, but it doesn't work so well on old OpenAL. I think I'll wait for the LeadWerks update to OpenAL-soft, so I can do things a bit more proper haha
For now I've implemented a very basic "dynamic" sound system which just uses two versions of the same sound, one muffled and with reverb and the other without those effects. This works well enough for now
Definitely going to look into a proper EFX implementation when the time comes though, I just love DSP stuff haha, plus it might help others too.