She wasn't shoehorned in last minute. She was in the Early Access from Day 1. She wasn't playable, and she clearly had quite a bit of rewriting over the course of EA, though perhaps not as much as Wyll. Comparing her EA version to release version and to her mtg card, the datamines that supposedly had a different usage for the soul coins, it seems likely the infernal engine in her chest was a late addition, which would explain how unfinished her personal questline seems to be.
The original plan was going to have Minsc as a good aligned origin party member, the plan from the getgo seems to have had a good-dominated roster, party balance be damned. That much has not changed, for whatever bizarre reason, although the exact composition has fluctuated.
