Illithid (Mind Flayer)

Well this one is a classic. I found myself struggling with it, because on one side I wanted to stay close to the image and feel of the original creature, but at the same time I wanted to make sense out of the lore of the Far Realm.
In theory the Far Realm is an incomprehensible assortment of dimensions inhabited by utterly alien beings not meant to be beheld...
yet most descriptions and depictions of illithids are pretty standard humanoids, if with a somehow alien mindset, a tentacled mouth and a taste for brains. I couldn't have that right? Well, I just played around making some modifications to the less speciffied details to make it look a little bit more alien.

-Super-Geek-Time Section Go:
SO. I´m -also-, of course, playing an Illithid, because: Illithids.
It turns out that following the level progression of only the monster class (as shown in Savage Species) is... meh. I really expected a little more. The limited HD and small pool of class features si almost crippling when I see my mates can do all sorts of crazy with a level 9-10 character.
Specially when fighting mindless opponents, I usually just levitate around waiting for everyone else to finish up the massacre.
As I've just now seen the Illithid Savant prestige class, it was inmediately and unanimously branded by everyone at the table as the most broken-OP class ever published in any manual (I must sort of admit it might be...). But I'm -really- looking forward to use it, it just makes tons of sense for the backstory of my characters (sent to this plane to collect information, strenghts and weaknesses about the natives by "working with them" to prepare an invation) to have a class that permanently absorves skills, knowledge and stuff from the brains it eats. As well hunting and collecting different brains and the skills they contain sounding as way too much fun.
Do you have any suggested fixes for this class? I'd personally like to work a way out to keep the permanence of absorved properties but maybe with some sort of handicap or limitation. Maybe having to succeed a concentration check when ingesting the brains and or when using the stolen properties, and or maybe preparing a limited number of them for each day in the same way a wizard prepares his spells, so I can't just freely spam all the properties I EVER ate at any time.
What do you think?