Witch hunter like profession?
With Ranger having a staff coming in the expansion, it might offer you the flavor you’re looking for.
I played a Witchhunter in Skyrim also.
Ice Bow Elementalist isn’t a bad idea, but the Ice Bow has limited uses before it has to recharge, so you won’t get much use out of it. Ranger is you’re generic pet class. It also has the ability to use magic to summon even more allies. (Oddly enough, this build, referred to as “Spirit Ranger” is very popular, and effective.)
Ranger sounds like it would be more your cup of tea. Also, its a user of Medium Armour, so it will be easier getting the witchhunter look.
Been a long time since I played Morrowind (and never got into Oblivion), but based on the description here http://uesp.net/wiki/Morrowind:Witchhunter#Witchhunter I might be inclined to go with a PU Mesmer if you remove the bow requirement and go with the baser requirements of “martial, magical, and stealthy”.
If you must have a bow, then I’d probably go with Thief although focusing on the bow there would be less than ideal. I wouldn’t necessarily go Elementalist either because the Icebow is more of a support weapon.