I may be necroposting here, but when I decided to go the "tactical 22" route, I looked at the Mossberg (until my LGS owner told me he would only do a transfer with teeth gritted) and the MP 15-22. I ended up getting a Ruger 10/22, and I have ordered the pieces to assemble it:
Ruger 10/22- wood stock/blue barrel: $250 after tax NIB
ATI Strikeforce 6 pos/folding stock: $70 used (Armslist)
Barska 30mm red dot: $40 LNIB (box opened, never used; Amazon)
UTG contour fore grip: $10 NEW (Amazon)
Single point bungee sling: $6 NEW (Amazon)
My total cost ended up being $376 including all shipping, taxes, and fees, and it has all the junk I would be putting on a 15-22 with a more versatile stock.
Moral of the story: sometimes it's cheaper to scrounge what you want and DIY.