Has anyone tried a RB5/Monkey hybrid?
 

Just wondering whether anyone has tried using one of the Ansmann/Team C mid-motor conversions on an RB5...

Why on earth would you want to do that?

There are several conversions out there for the RB5 (MCS/Scorpion/VEGA in order of release) which have all been proven to drive well, no are massively expensive either.
Scorpion even allows you to switch between mid and rear motor in around 10 mins.

Surely it's not worth anybody doing a chassis to mate the Kyosho suspension assemblies to the Ansmann gearbox?

To that I could say why spend the money on one of the mid conversions, when the TLR 22 is under $300 and kicks ass? (other than the fact that I'd still rather own a Kyosho over the Losi I bought last month)
Not everybody wants to buy someone else's creation. Other people are just as interested in creating something for themselves, as you were when creating the Scorpion.
I'd say if you're up for it sosidge, give it a try. I'd love to see the results!