This is a product that I am surprised hasn’t been developed before now – a hand guard extension.
A company called Alien Armor is set to produce a product called Rail Guards that are sort of like a cross between a rail cover and a stand-alone polymer hand guard. It attaches to an existing hand guard via the side rails to serve as both a rail cover and to extend the length of the existing hand guard. If this attachment is robust enough, it could have some interesting applications.
The Rail Guard appears to feature M-LOK compatible slots or something very close. Even if they aren’t M-LOK compatible, direct-connect accessories like those from Impact Weapons Components would likely still work.
Alien Armor is already advertising broad compatibility for the Rail Guard. They state that it will fit many AR-15s, SCARs, Galil Ace, SIG 556, many AKs, the CZ Bren Carbine, ACR, XCR and more. Basically, if it has side rails on the hand guard, there is a chance it will fit.
The Rail Guard weighs 7 ounces. It is not available for purchase as of the time of this writing but may be available in as little as 3-4 weeks. Stay tuned for updates.