But... they can also sell expansions that includes the best models... if they keep the control of the add-on or integration with official game patchs.
Don't know how was done on IL2 comunity... may be they published the 3D desing requirements, and the game developers were responsible to integrate only the best-quality vehicles in a official patch.
May be what they need is to open a SDK to explain the poly limits, etc... and then the community can work under those bounds to submit their work to expect it included in the next patch release.
A lot of people will make good quality donations, and the developer team can reduce his load of work by several orders of magnitude.
Is a fact that the number of hours needed to model those high detailed units, are a lot... so, we will never se a game as much complete in units like the old CM. Will be a pity if this engine puts a limit on the diversity of units that we enjoyed in the earlier versions of CM.
Please, consider the way of expansions with some player base colaboration that was done with the IL2 series.