Are you playing on hard? If not then Glass Cannon is viable on everybody, just be aware that with 20 AP/turn on 4 characters there won't be much challenge at all. Otherwise Lone Wolf is essential to mitigate the HP penalty.
For a wizard LW/GC you could go full elemental (air/water/earth/fire). Checkout [url=http://divinity.wikia.com/wiki/Divinity:_Original_Sin_Skills]the wiki for skills[/url] that you like and prioritize what school you need to raise first.
Note: a high ability score allows you to scribe more spells in your spellbook and cast the higher level spells without penalty. It doesn't make skills stronger.
Then you could raise leadership to boost the physical damage members of your team and their initiative. Later down the road you could boost willpower and bodybuilding for better saving throws.
You don't have to raise all abilities to 5, just enough to get all the skills you want in each element. In a pure zap-from-the-backline wizard you don't need spells that put you close to enemies (touch spells,
Lightning Strike,
Self Immolation etc.), so you could save points to put into passive abilities.
In my case instead of earth in the above build I went man-at-arms. It's strong but since he needs to be good in *everything* I had to go with double leadership and juggle attributes to keep him viable on all fronts. The former build sounds smoother in retrospect. :)
That's a bit of a wallo'text already so I'll wrap it up with a new
2Pac song.