Speaking of GJ-X being unmanned arsenal aircrafts for AAMs, similar ideas have indeed been brought up on the other side of the lake just a couple weeks ago:
So, yes - Something like the GJ-X should be able to carry at the very least a few AAMs inside its IWBs. And given the overall length of the center-body (~22-24 meters), the GJ-X can actually have an IWB that is ~9-10 meters long.
This would mean that a at least couple PL-17s could be fitted inside the GJ-X's IWB. Though, if we want to go further and utilize the full length of the IWB, that would mean XLRAAMs in the high-hundreds of kilometers (>600 kilometers) of maximum strike ranges. Otherwise, a 9-meter long IWB would enable a longitudinal dual-stacking of PL-15/16 LRAAMs.
This hasn't yet touch on the possibility of either a rotary launcher or vertical dual-stacking of AAMs inside the IWB, but that's a discussion for another time.
In the meantime, though - I'd prefer something in between the GJ-11/21 and GJ-X in terms of dimension, MTOW and payload capacity for such roles. This should make the platform not just being a viable and significant upgrade in terms of payload capacity and range/endurance over the GJ-11/21, but also not as expensive and is less prone to attrition than the GJ-X to enable procurement in greater numbers.