What your reason for wanting to shoot ISO 100 film? If it's to deal with brightly lit, high-contrast scenes, I think you can get by just fine with a single film.
TMY2 performs beautifully at EI 400-800, processed normally in Xtol, yielding normal contrast negatives with its famous grain and tonality. If you want higher contrast, you can push process it at 800, and you get even a little more contrast (and grain) at EI 1600.
As for the low end of the scale, it performs nicely at EI 200, with a little more grain but nicely reduced contrast for those harsh light situations where you might otherwise wish you had an ISO 100 film.
I don't stick to TMY2 100% of the time, but probably something like 80-90%. The other 10-20% of the time is when I'm reaching for TMX, TMZ K64 or Ektar. But if I were to lose the other options, it wouldn't be the end of the world.