In a way, the B-21 employment doctrine contemplates the launch of stand-in munitions.I highly doubt the US doctrine sees the Raider go over mainland China and dropping dumb bombs. Rather it will be the launch platform for whatever system comes out of the USAFs efforts to field a hypersonic ALCM. Which gives it significant stand off range and doesn't make it necessary to leave the friendly AD umbrella provided by naval assets and aviation.
The B-21 will operate alongside the re-engined B-52 as a Hi-Lo Mix (High and Low Performance) duo. The B-52 will be tasked primarily as a “missile truck,” launching salvos of cruise missiles outside the range of enemy defenses (stand-off strike) against fixed targets; while the B-21 will act as a penetrating bomber and launch salvos of missiles and bombs already within range of enemy defenses (stand-in strike) against hardened, mobile and relocatable targets that are inaccessible to the B-52’s cruise missiles.
The point is that the J-36 can act as a B-21 hunter in the 1IC.