Going through the mages guild again I realise, as I have many times before, that there isn't much to do in Caldera. Is there any good mods that changes that, maybe gives Folms Mirel something else to send you off doing except find all the pylon indexes?

I believe Magical Missions adds about 4 quests to Caldera Mages Guild. Also not exactly mods that offer you to do more, but are also related to Caldera MG - there is mod that adds one uderground level with beds for members. Nothing over the top, just beds, since there were none in the guild. And there is also mod that removes the unguarded master alchemy apparatus from the tower.

EDIT: http://www.nexusmods.com/morrowind/mods/38773/? and http://www.nexusmods.com/morrowind/mods/43733/?. Could not find the last one now.