You will have the same problems as in previous version, I'm afraid.
This install order with BGT first is needed to ensure BG1NPC always changes correct dialog states. V12-Beta had errors (regardless of install order) in dialog state numbers so that BG2 dialog states or mod-added states were changed instead of BGT ones.
I've discussed the possibilities of removing this install order requirement with cmorgan, but we decided it's too much effort for nothing, because: a) it's very complex thing to do; B) BGT will still work perfectly no matter if it's installed before or after TDD (or other BP family mods).
I mentioned this in the current stickied Erebusant's install thread, here, but I guess it's not easy to find now, sorry.
What if I removed BG1 NPC before speaking to Belt? Would that do the trick? I guess I would like to try to find a way to keep my current setup without a whole re-install, but if BG2 will be unplayable then of course I will just re-install.