….130mm axle and spacers from old 105 hub (keeping original XT cones and locknuts)

Should be OK shouldn’t it?

I’m intending building up some sturdy touring wheels for 130mm spaced disc brake specific road bike but 130mm disc hubs are hard to come by and the current 24 spoked rear wheel is probably too risky to carry too much weight on.

You’ll be losing the extra 5mm from the brake side as there’ll be no clearance for the cassette by removing any drive side spacers that may be there, I suspect you may then run into disc alignment issues. Try it first by just removing 5mm worth of spacer from the XT hub to check for any issues.