Just installed BGT, having never really played the entire game (played a bit of BG1 years ago, played a good... 1/5th? of BG2), started a new game, got to the Friendly Arm Inn and... I still hate Jaheira! And this time I can't just leave her to rot in a dungeon and pretend my Neutral Good character didn't see her. Damnit, Gorion, why would you do this to me?

LOL as any good parent he used guile to set you to (what he thought to be) the right path.
But from a roleplaying perspective I think you can find a reason to dump her -and Khalid... or you cheat!

What I always when removing NPC from the party is:
-I make sure their spell selection is appropriate for a generic encounter.
-I refresh memorized spells with a good rest.
-I give them tolerable quality equipment (that I don't need of course, generosity goes so far)
-I kick them out in a tavern (in lieu of mods that send them there on their own)
-I tell them it's for a little while and to wait. That I later "forget" is completely irrelevant.

See? No teeny bit of guilt.

Jaheira is probably my favourite female character in BG2. She is a bit of a bore in BG1 though, and not too useful to boot, so I can understand wanting to kick her out in that game.

You could always 'accidentally' put an arrow or a sword through her gut.... :p

I'm going to use her and Khalid as tanks and drop her when she dies. How will this work with BGT and going into BG2?

I believe with BGT installed she won`t be in the cell in Irenicus` dungeon if she had died in BG1.

Excellent.