Everyone wants more adjustment settings and a "gas-off" setting is great for suppressors and accuracy.
A gas block with quad rails is a seemingly obvious choice. Just make sure it can be made to work with the AXR!
There are a few issues with this idea. First of all, if the thing you're holding onto is hot, you're going to want to let go. This would necessitate insulating the rails from the block itself somehow. Secondly, I think the gas block needs to be made out of some sort of steel, not aluminum. A one-piece quad rail gas block would be quite heavy. Last, if you put a rail on the right side of the block where the piston is, you create the problem of not being able to get to the piston.
How to overcome these issues? I wonder how far you could get with the idea of putting a clamp-on free float quad rail on a custom steel gas block. BOBno1, have you seen the way LWRC uppers are set up? The top rail is removable for access to the piston. I think a setup like this would work excellent on the AUG, with the removable rail section flipped to the right side, especially since you could have one block and swap out different lengths of free-float rail depending on your barrel length. If it's big enough to swallow a Noveske KX3 or a supressor, even better!
Another good idea is to make the block compatible with an existing AR-15 adjustable regulator, and to make your own piston which would use any gas rings that work with a DI AR-15.