A gold dragon or a silver dragon companion that helps the group disguised has a normal humanoid companion ( whatever the class), with multpiple occasions to unmask its true nature via dice/dialogue chacks.
It seems obvious but dragons are an absolute must be. Red dragon would be awesome. I loved Fiirkrag for everything he represented. He was a walking vanity, his wings attack would be epic if only animations weren't so inexistent back then. I would love to see a red dragon just "flush away" my team while slowly walking in the opposite direction.
I always wanted to learn more about Mind Flayers but we kinda have too many of them now lol.
And demons. I loved their riddles.
Alt+ left click in the inventory on an item while the camp stash is opened transfers the item there. Make it a reality.