I've played men of war plenty. They used a lot of the prototypes for that game, but that's also mostly because they don't have abilities and has more realistic machanics then COH. If COH added them they wouldn't even need to go that far if they used the abilities and structures well, but I wouldn't mind seeing a few prototypes.
The guys who make world of tanks actually found out that one of the prototype medium tanks they had built the chassis for was planned to have a autoloading gun. Would be cool to have such a unique unit in the game.
Edit: Here is the source on the autoloading Chi-Ri:
http://ftr-wot.blogspot.com/2013/05/chi-ri-imperial-japans-most-advanced.html