Yes, as I said, I like that option and enabled it in this playthrough as I do usually in normal XCom. Since in vanilla you can start stupid low, it goes all the way to 100 and a campaign is generally less than a year, I've never had balance issues with it. My psi-weak soldiers never really catch up with the good ones, at the very least not to the point where they become worthy psi-users themselves.
In Piratez, I've had voodoo schools for more than a year, so the training has added up, to the point where my weakest psi-soldiers are now at the cap like everyone else. I don't encounter psi enemies much (just got my 2nd esper so I can break one in late 2602, haven't seen a provost yet) and can't use it much (no witch outfit :/) so I never noticed, then yesterday when sorting troops to take on the academy pogrom, I realized this had gotten all screwy. Gotta edit my save to bring the psi power training down a notch.
Thinking back, a relative cap isn't necessary, although it could be interesting (defined as a %? like str: 1.5 means you can add 50% to your starting strength, then rest you need to train in the field for). But for psi, the ability to define a cap is all that's really "needed" for me. Something like 40 str, 10 skill, and the rest needs to be trained in the field. This gives a further reason to have wands and odd voodoo outfits, which I have overlooked until now.