That Osprey Defense kit is very intriguing. No need for a new gas block it appears. Might restrict handguard selection a bit though?
Mine came with a hand guard and there are several on the market which fit overt he piston cup. That thing is virtually self cleaning. I shot the three hundred test rounds through it and when I went to clean it it was clean! You do not lube them so no gunk tends to build up. I expect after a couple thousand rounds it should be cleaned with a bruch and hoopes 9. The kit comes with a handguard, the piston and cup and the bolt carrier. You use you own bolt installed into their carrier. Very efficient system and seems to add no weight out front since their piston cup has a tube which replaces the existing impingement tube in your gas block. The handguard does get hot with a couple of 30 rounds mags, but a vertical foregrip or AFG solves that issue.