You're comparing apples and oranges there. Of course trucks have modular systems - they whole reason they exist is to carry all sorts of different things. That's why they have a flat bit on the back.Why would we buy more modules then trucks to fit them on, why would we buy more modules then there is room on the ships for them. We do so to increase or decrease on an as needed basis (as I understand it) and that same approach can very well be useful with the future CRV.
As a blue tag you are more knowledgable then me but cnsidering the way we have been moving in acquiring other modular capabilities short of a crystal ball I don't see how you can garauntee with 100% certainty so for the mean time how about agree to disagree?
An armoured fighting vehicle is a very different thing. What are the circumstances you would want to change out the mission module on a Boxer? I can't think of one. The mix of variants has been specifically chosen to provide the capability required. Except for a first principles change of the Orbat of the Army, why would you need to change the capability mix?
Perhaps you can highlight a practicle application of this? How specifically do you foresee this modular system being useful?