I have a couple of AA uppers from when I was on the piston bandwagon. Curious about installing DI barrels on the uppers. The gas tubes seem to fit through the op rod holes. Am I overlooking some factor that would make using these uppers for DI a really bad idea?

The AA gas blocks are pinned to the bbl. I don't really understand the question if your asking about using a stripped AA upper?

Using an AA upper receiver with a DI barrel should pose no issues

I converted my DI barrel to GP.
You just have to line up the gas port correctly to the hole. No biggie

I assume you are wanting to use the AA upper to build a DI AR15.

I believe the OPs concern is that a AA piston upper has different dimensions compared a DI upper. The deviation would be located within the gas tube channel of the upper receiver. Per AA website: "Receiver hole has been cut to .180" eliminating the need for a receiver bushing".  The AA retrofit kits use a bushing on the back end of the upper gas tube hole in the upper. So that is what would be special about a AA piston dedicated upper is that the hole would not have been bored out.  In a DI upper, this hole is much wider.

I do not know for sure, but the gas key on the DI BCG may crash into that inside part of the AA upper.