Thanks for your long and detailed reply, it makes it difficult to come up with a proper answer.

I see the issue mostly from a economic and logistics point of view. There have been over the years quite a number of successfull families of military vehicles, some of them in the combat role. In general the variants of the same family share a good part of the chassis, the power train etc. while differing only when the specific requirements of the specific variant demand it. So far so easy. The key benefit is that the whole is more then just the sum of the variants. It is also a sort of benefit which is difficult to integrate in a trial of a specific vehicle/platform so that sometimes the individual winner is worse for the whole then the second or third-best. Nothing new there, of course.

What I personally find interesting is the fact that historically the heavier combat vehicles like MBTs , SPGs and (heavy) APCs seem to have remained rather isolated members with little share in common. Yes, there are many specialized vehicles bases on MBTs but seemingly hardly one with considerable volume.

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Anyway from a technological point the hybrid system of the GCV does sound interesting, it sounds like a parallel one.