TMX is only two stops slower than TX. Which in portrait photography might be also an advantage.

Hm, I am in Toronto, and believe me, I didn't see the sun for two weeks now and so will be on for the next few months. Yet my base film is only ISO 250 and often I shoot at 160. For most static subjects ISO 100 will be sufficient in most situations. Just try it.
Most modern emulsions will respond well to less aggressive developers, using lower pH. The other factor would be less silver solving action. Structure of grains of silver halides in emulsions became more "sophisticated" and (modern TX is not the same film Ansel Adams new) there is virtually no need to use ultrafine developers. I have better results using Dektol than D76 with TX. The whole idea is to not to over develop. That will preserve the delicate tonal separation and apparent sharpness at the same time by keeping the silver grains only at minimum size and nice shape. This will eliminate the need for solving silver action, which, in case of D76, will leave the grains of silver sponge like and with jagged edges which works against good tonal separation and acutance.
Rodinal has too high pH for TX causing non proportional development of grain. Again it works against tonal separation by increasing local contrast and build uneven grain. But higher pH of Rodinal will work well with Tmax 100.
D76 has way too much sodium sulfite which will dissolve a lot of silver from already formed image. With known effect.
The whole thing requires a bit of conscious experimentation to have a fun with it, but then, "fun" has very elusive meaning.