Well, the system had to be able to handle bigger numbers because the various bosses were using them, either in their attacks or in their stats, or both. Since a continued progression is probably easier to code than entirely new abilities, there was a chance the caps applied only to levelling choices and could be sidestepped.
A mod that might work would be a replacement in-game level-up tool that tracks high XP for levels 30+, gives you the appropriate stat/hp/vitality and 'points' and edits in the changes you select on spending them. Sort of an integrated CE table, except only giving you the appropriate point/stat amounts. As I said though, I got no programming knowledge on how to make something like that.
And yeah, I always was a fan of the sorceress.