Colin is the lead so he gets the final say, but the DM and SE were designed and built from the ground up. I think Colin's intent here is best described as take something and bolt it on something else that was not really designed for it.
So add a flame thrower and fuel trailer from the Churchill, to an M4 Sherman and make one of 4 given to the US army to use.
Add a dozer blade, flail system , 'Aunt Jemima' mine roller system, etc to a Sherman
Bolt a panzer IV turret on a Bergepanther
Bofors mounted on a GMC truck (French)
Add a Mig 21 engine to a T-55 chassis and make a fire fighting vehicle... a darn quick one I guess
Just about anything the Israeli's did with old vehicles would fit the bill I guess - Achzarit, Puma, Ro'em, etc
Maybe even conversions like the British Archer and Bishop and German use of French tanks chassis and so on.
The list could go for pages, but if I am right, what Colin really wants to see is people finding obscure conversions and one off's to make the choices really interesting:
French Chaffee with AMX 13 turret
Russian Concrete armoured T34
German Pak 38 on Renault UE
Chinese Japanese 10 cm artillery equipped M10 GMC
T105 Sherman rocket launching tank