Aside from bugs you're planning on fixing, if you're able to, I'd suggest that you make new Forge menu strings for the Reach weapons and vehicles (that don't have vanilla counterparts) so they're easier to distinguish. Something like "Assault Rifle, Reach" should do the trick.

I also do think you should consider putting this in the Remember Reach pack to reduce overall file size, once you've got it finalized. Halo 3 maps are particularly bloated when you don't build with shared resources, after all (I'm guessing 'cause of the new armor that was added in MCC). Maybe you could add the R3ACH weapons to the other maps' Forge palettes, too, if there's room for them there.