Working for me on co-op now - turns out my friend somehow managed to install this mod incorrectly on two separate occasions (despite having installed WaW maps before). Everything is now working perfectly; didn't need to verify my game files or anything either.
 

I had a similar co-op error to the one above, with a mismatch for the Tokarev and also for the PaP version of the M1 Garand w/launcher (that I know of). I don't have plutonium installed (just T4M), and I've been trying to find a way around this but with no success so far. If I can find a fix, I'll post an update here saying what I did.
 
Other than that, I've got Der Riese installed and had a blast with it in single player. Best remastered map I've played by some margin.

Looks pretty great so far! I really like the fact you're trying to keep the feel of the original maps.

Will the Type 99 be on all maps or just Shi No Numa? Same with the Mosin Nagant and Der Reise.

I know these weapons also have PaP variants in the game files, so it would be pretty interesting to see the Type 99 in Der Reise