I'd say two wizard 20s can probably handle most campaigns, but of course, that's not what you're looking for. Else you wouldn't be in the CO board.
You have a summoner in mind, I'd say that's a good idea, but by no means take my word for granted, as I'm fairly new to the world of optimization. If so, you should specialize(focus-specialize?) on conjuration and take Abrupt Jaunt, from the PHB2, losing your familiar is a pretty cheap trade for this. Also look into the conjurer variant from unearthed arcana, so you get augment summoning instead of scribe scroll at level 1. You could go the Master Specialist route, but then I'm not entirely sure it'd be better than just straight wizard 5. You'd get an extra feat by then, unless you have some specific low-level conjuration spell from another list you want, or plan going into archmage later.
If you want to get cheesy, you could take sanctum spell and enter it at level 3. By level 5 you'd get greater spell focus conjuration, and if you got iron will, even be able to go right into incantatrix. Something like Wizard 2/Master Specialist 3/Incantatrix 10, or maybe some malconvoker in there if you'd like to. In fact, two of those incantatrixes would just destroy everything on their path probably. If going that route, and you think incantatrix 10 just won't work or something, tough it is a very very solid build, you could go incantatrix 3/4 and then Malconvoker or maybe Shadowcraft Mage with the other.
You could have a gish too, tough I'm not too well versed in their building blocks, it should go along with abjurant champion, for sure.
I'm still more inclined to the two incantatrixes, with a little flavor on the mix too. If going for a SCM, I'm also pretty sure there's a shadow adept or something of the like on the player's guide to faerun, and then there's shadowcrafter. Both should help an illusionist in making.
For now that's it, maybe I'll come back for more
~~Aliek
