oooo...a debate
That Int progression is too aggressive...the Grand Aboleth is going to end up far eclipsing great wyrm gold dragons, archdevils, demon lords, and most deities!
I'm OK with boosting mental scores a bit more, but I'd like to retain Cha higher than Int for each of them, as they are heavily SLA/Cha-based Su ability focused.
To their defense, they are also older than most deities. As for the Grand Aboleth, it depends on how you end up setting them up. The jump to 40 HD, and all racial, would be too much, IMO [I prefer 26 HD, but that debate is for when we get there ;-)]. Remember, 2nd Ed. didn't really take logical progressions into account, they went with what felt right with little regard to how it would get there.
I also disagree that the Aboleth is a creature of Charisma over Intelligence. Now, granted, the SRD has 15/17/17 and you want to keep that base line, it doesn't mean it must stay that way. Spell-like abilities are keen, but these monstrosities are geared to be Wizards and Psions, not Sorcerers and Wilders.
If you equate each HD after 8 HD to equal approx. 200-250 years, it is not that aggressive.
They were created by an elder evil.
They are mentally more evolved than dragons.
They have all but taken over Stygia. (I may be exaggerating a bit

)
For icing.....Genetic Memory. ;-)
Long run, aboleths should be mental (read INT) powerhouses.
Bykov.