Enslave (Su)
I have broken down Enslave into (5) aspects. The first two I think are pretty straight forward and unless there is a differing opinion, I will go with them.
#1 - Resistance to Enslave - Enslave's duration is indefinite, but the target is allowed a Will save every 24 hours to attempt to break free. I do not see that 24 hour window expanding over the age categories.
#2 - Similar to Dominate Person - With our choices of dominate person, dominate monster and psionic dominate, it seems that mimicking dominate person is the way to go. This also allows easy translation between a psionic and magically based creature if so desired.
The other (3) aspects are Range, Creature Types Affected, and Times/Day:
Range
Standard is 30'. As with the ecology article, this range expands with the greater aboleth. So sticking with 30' across the board seems restrictive. I believe that increasing 30' per category would be excessive, especially considering the Enslave ability would then extend beyond the aboleth's telepathy at higher ages. So I think the options are:
A - 30' per age category and increase telepathy 50' per age category, or
B - 30' + 10' per age category, giving the aboleth 40' early on and 100' at the most advanced age category.
Creature Types Affected
I am thinking humanoid plus one other type per age category. This could give a common aboleth humanoid and monstrous humanoid, while a greater aboleth could have humanoid, fey, and giant and a grand ruler (category 7 in the second progression) could have humanoid, monstrous humanoid, outsiders, fey, giants, magical beasts, aberrations, and dragons.
The other option would be to give a limited number at the beginning and leave it as such. I can see applications for humanoids, monstrous humanoids, fey, giants, aberrations (not so much...but aren't skum aberrations?), and outsiders.
Times/day
In the ecology the common was at 3/day and the greater was at HD/day. I am thinking HD/2 per day. This would put the common at 4/day and the grand ruler at 16/day. Or to have the start point line up it could be HD/2 minus 1 per day.
The other option is to stick with 3/day but add the ability to do multiple targets at once, but I think that would be very overpowered for any monster.
As always, your input is greatly appreciated Freyar (and any other lurkers out there that would care to chime in

)
Bykov.