lol yeah that's where the crux of the matter lies for me, I don't like applying one rule for PCs and another for the NPCs.Just don't make them too powerful. If your Talosian analogue knocks your players' Type A out of orbit like swatting a fly, the players will either want to be Talosian analogues ... or go away and play Traveller somewhere else.
Atm I've decided to go for the rule as presented in the psion book, with the space opera style (x1.5 PSI). This means that a typical Psion with a 9 (+1 DM) total PSI would end up with a 14 (+2 DM) in the end, and a maxed-out psionic from a powerful psionic race with Psi 17 (15 max +2 racial) would end up with 26 (+6 DM). This is offset by the normal rules on max powers per day being half the INT score, and that effectively after every single use of powers (since in my dredd game a PSI Judge never used less than 2 points per use) the DM would drop quickly.
This means if the players tackle a psionically powerful alien, that alien's first few minutes will be very dangerous for the players, but if they hold out then by attrition they'll quickly wear it down.
Part of me balks at seeing a +5 for a character's psi stat (esp with everything else at -1/+0/+1) and thinks that it may just be easier to use the whole thing as a Psi pool and keep the DM the same regardless of how many points they have. After all, other players don't lose INT or STR from using it a few times a day... And they already have restrictors in the form of daily power usage and trauma levels.
I agree with you totally that I might bring in some alien monster with off-the-scale psi power, and I may give it whatever I want, probably enough to scare the players... but this would be the exception, not the rule. It's the rule I'm worried about.