If you re-amp to get the binaural image, then you are of course introducing the coloration of that speaker. But since guitar amp coloration is the goal, reamping could be a valid solution.
As for me, I’d like to try some binaural transformation plugins. Virtuoso can simulate loudspeaker locations in space from stereo (or immersive) mixes, including those made from panning close mikes to positions. Maybe it can do a good job with the integration of a binaural mike with spots. Feed the spots into virtuoso and mix that with the existing binaural mike. It’ll probably be a mess at first, delays and all have to be aligned as well. Have to put your ears on and work until it sounds convincing!!!!!