technically, but there's no real reason to. Most of them are either useless or redundant, with very few spells actually being worth casting. A sorcerer can by careful spell selection, cover every possible situation, while a mage is able to learn a bunch of extra spells that have no use or are weaker then other alternatives.
Were this PnP and had all the options PnP allows, having more capacity would be a good thing, as their are TONS of options available to use, and the utility based spells are just plain more useful. In BG however, you don't really need the extra capacity nor will it ever be useful.
It mattered more in BG1 (vanilla) cause you can't erase spells...but in EE and BG2, you can...so..no reason at all for capacity.
Technically speaking a Conjuror's opposed school should've been Evocation (they only lose access to 3 divination spells in PnP (all divination above 5th and above...since 4th and below is absolutely critical for functioning as a mage...it's why they removed divination completely as an opposed school in 3rd and 3.5))..but all of Evocation (on the other hand...most specialists were supposed to lose 2 schools..except Divination (1) and Illusion (3))
If this is a goal for your main character all you need to do is memorize what you can, store the rest in a scroll case. Then down the road just adventuring and exploring you can possibly find a tome that increases your INT by 1 permanently. Assuming you have 18 int already, you can just read that and BAM, you can start adding more spells.
Comments
Were this PnP and had all the options PnP allows, having more capacity would be a good thing, as their are TONS of options available to use, and the utility based spells are just plain more useful. In BG however, you don't really need the extra capacity nor will it ever be useful.
It mattered more in BG1 (vanilla) cause you can't erase spells...but in EE and BG2, you can...so..no reason at all for capacity.