"Gifts might just be better than Thirst, though. I considered a 3rd Jace in that slot as well."
Intuition might be preferable, no?
You can't combo intuition with welder and bsc though.
No more than you could with Gift's Ungiven.
I love Intuition and I believe each of the three cards mentioned, have merit. Gift's and Intuition are both great with an active Welder. A third Jace, however, increases the threat density while providing many options. All three could fill that slot, and Thirst is fine too. It really boils down to the metagame and a bit of personal preference.