In the Beltbrd.dlg file however, Belt is a jerk and he wants to get rid of you because the other nobles are restless about you ability to kill a Bhaalspawn. It makes them nervous. This is the only version of Belt that I really remember, I always thought Liia did the talking during the Sarevok coronation. Anyway, the two Belts don't seem to be the same person.
So, I rewrote the Beltbrd.dlg file so that you have a few more options. Belt now tells you about problems with Athlatka and Amn. They still want to go to war with Baldur's Gate. He is trying to explain to them what happened but no one will listen to him.
So, he has two problems now. He has a person that can kill Bhaalspawns and he needs some to go to Athlatka to setup a special meeting for him. Enter the PC.
He will now explain the situation to you and tell you that he is going to teleport you to a forest just outside of Athlatka. There, you will meet his contact, someone who even requested you (hehe). Once you agree to teleport, you will begin the normal transition cutscene that kinda/sorta works.
This is just his dialog, I didn't mess with the scripts, transition area or any other files. But I think this may be a little better solution than the dialog Belt gave you in the past. You still will not be able to start SOA until you accept the teleport from Belt, but at least now, you can continue with NTotSC or whatever else you need to finish before transferring.
By the way, you still need to go solve the TotSC quests. NTotSC requires it anyway but even if you don't have that mod, I haven't editted Belt's check on completing that quest. If you can't stand the TotSC quests and want to skip them, I can add the one global setting to this dialog to skip that quest (or you can do it yourself).
Since this is a D file, you need to use DLTCEP or Weidu to import this into your game and overwrite the current file. Please take a look at it (it is just a text file) and see if this storyline sounds better to you. Unless the Transition Mod that Ascension64 has done also modifies Belt's dialog, I would assume this will work with that version but I don't know. Ascension??