It isn't as easy as you think. Simply allowing to unsetup would have to return resources. Which is very abusable. On top of that, both of your propositions make okw stronger, which is unwanted after all the ballance fine tuning we got. And yes, it is your preference as most people agree coh1 brits were the worst designed faction in history of coh2. Nobody wants them back. People even got scared by the okw just when they saw okw has some forward setup trucks becouse they thought it is going to be as bad as coh1 brits.
I won't interfere in the balance discussion, just want to explain what I have in mind (and which will be implemented in the all units mod very soon).
The player can buy three different trucks, which can by recognized by their different symbols. The costs are the same as the current implemented truck + building. Losing a truck that way will be a game-changer. Setup and making mobile will be free and therefore no refund is needed and it cannot be exploited. Once you make an HQ mobile, it can only set up as the type is was before and thus not skipping tier to get to the last.