I was thinking of going through the game with Immy as only Thief and only Mage in the party ( Ranger, Paladin, Viconia ( Cleric ), Imoen ( Mage / Thief ) and Sarevok...
But I think Imoen cant be excellent Mage and Thief at the same time, so I want to make her Multi-class Mage Thief, instead of Dual...

Well I need help, how to do it ???

Use shadowkeeper.

She will do just fine, if you have read any of the other threads concerning her. ;)

Shes great as a mage, as a thief she gets the job done. Not like Jan, but she's able to do what she has to.

You think that she can do the job, without any edit ?? Well, I give it a try then :D :)
Thanx :)

She can definitely get the job done. Just hold onto any "thiefy" potions in case you run into a problem, but these will be (very) few and far between.