A lot of these discussions seem to pop up every few years. I'm migrating more to the idea that the USMC uses, where things like the vehicles are not even "Regimental" assets at all, but in our context would be a Bde or Battlegroup asset, essentially its own unit. This would certainly allow for many mix and match combinations, you could imagine a light infantry deployment, but giving Engineers section carriers because they need to cover a large area. Of course the argument will arise that you will have a very large and resource intensive unit since you would theoretically need to be able to mount up everyone at once, but rarely do so in practice.
What is the sweet spot? Should we have enough assets to ensure being able to mount 66% of the brigade at any given time? 33%? 25%? This can also give rise to other combinations - if we have enough LAVs to mount 50% of the battlegroup should we get enough Bv-10's to mount the other 50% (providing lots of flexibility to move the battlegroup mounted through the arctic or other marginal terrain). Separating the vehicles and their resource management from the units opens up different possibilities.