Well, the patch didn't take as long as I thought. When loading scythe 2, load Babel, then Scythe 2, then the "Babel Compatibility Patch - Scythe 2.pk3" you can find in the "Babel Addons and Patches.zip" download and you should have Afrits and Evil marines that can be shot with the BFG9000.
The Afrit still fires baseline Revenant shots (because I'm not sure of the balance with the new ones) but otherwise they should also use the new projectiles and have particles and such. Evil marine doesn't have extra gore on XDeath but that's mainly because I'm not sure how to do it in a non-messy way in Decorate right now. Might change it later.