Fighter to Mage or pure Mage

First off I will be playing only multiplayer will a full group of friends once bgee is released. I volunteered to be the groups mage and was wondering what you all thought my best option for filling this role would be.

my initial thoughts are to either make a gnome illusionist or a human fighter and swap to mage early enough to still have all the mage potential sense we will need it late in the game

any and all thoughts are greatly appreciated and thank you in advance for your sugestions