Improving an Aboleth's feats.

[Tvtyrant]

The Aboleth is one of the iconic D&D monsters, but the SRD Aboleth has crudy feats. Alertness, combat casting and iron will are all awful feats. I'm trying to make an Aboleth capable of holding a city of Kua-toa hostage by its lonesome.

I am thinking of swapping one of them out for Boost Spell-Like Ability, any suggestions for the other two?

[Da'Shain]

Improved Init and Power Attack would seem like the standard ones. Or go with Ability Focus if you want to make his Enslave ability even more threatening. Quicken SLA for one of his illusions might be useful, probably for Hypnotic Pattern so that he can Hypnotize and Enslave all in one round. You going outside core?

[Tvtyrant]

Yup. Just about any splat is open. Ability focus would combine well with Ability Focus, driving the DC up by four.

[Lateral]

They only get three, so there isn't really that much you can do. Binding feats, Incarnum feats, or Martial Study/Stance are probably your best bet. Their spell-likes are nice, but not all that useful in combat.

[Waker]

Well, if you use the Psionic Aboleth (http://www.d20srd.org/srd/psionic/monsters/abolethPsionic.htm) in Expanded Psionics, you might consider some of the psionic feats like Expanded Knowledge.