Caster: I like having an enormous variety of spells on hand. I find it difficult to choose a spell school I would drop. I think with the extra points from Lone Wolf, taking all 5 schools is the way to go. I don't think I would change a thing.
Consider carefully whether you gain all that much from skill 5 over skill 4 for each school. You almost certainly don't need to know all spells from all schools (though I guess it might be fun just to say you did it), so you don't need 5 for knowledge (in some schools, even 2 or 3 might be enough depending on your focus), so all that matters is which spells you are okay with paying a small surcharge in AP for and whether you are interested in any of the skill 5 talents.
For only 15 points you can pick up man-at-arms and get the Picture of Health and Weather the Storm traits, which will make your caster considerably more durable, something of some importance when running two characters rather than four, where your caster will more frequently come under attack.
(Also Opportunist and Sidewinder, but the first doesn't help your defence and the second is marginal).
