As Kadonny said, the A2 stock requires a different receiver extension (buffer tube), spring, and buffer.

If I understand your question, you are asking if it is reasonable to have both setups and just switch back and forth? If so, then yes, that is unreasonable... the castle nut on the carbine stock should be staked in place by the end plate. Plus, each time you want to change it, you run the risk of losing the detent and spring that keeps your rear pin captured, as well as the buffer retainer.

Think about it this way... pull two pins and you can put a different upper on your lower, yet most end up getting a second lower to make two complete rifles. What you are suggesting is more complicated than just pulling two pins... With the laws in your state, your best bet is two different rifles, or at least two different lowers configured how you want them regarding different stocks and LOP.