I have an MOE model to go with a bunch of AR 's including a DPMS in .22 LR. The little M&P is about as much or more fun to shoot than any of the others, just remember it is a plinker and not a match gun out of the box. It is funny displaying photos of .22 ammo and I guess indicative of the times, I keep tens of thousands on the shelf and have for 40 years but did not realize I was a "hoarder". Grand kids need a .22 to shoot when they visit grand pa......I think that is written into the Constitution somewhere :-)
Shoot your 15-22, enjoy, and then add accessories when they are well thought out. Thus you will save yourself bunches of money on stuff that eventually would later fill the parts drawer.