Well, I don't agree with some of your assumptions.
First, in AD&D (1E) most people who had psionics had very little and it left you vulnerable to special psionic attack modes etc. that non-psionics were unaffected by. Only if you were really lucky and had good INT, WIS, and CHA were you likely "more powerful" for being psionic.
Ok, you realize that since my complaint was with random systems for powers, that a result of "you rolled well enough for special powers, you are now
weaker and more vulnerable to attacks" is even worse than being too powerful, right?
Looking at this you would need to roll good Int, rool good Wis, roll good Cha then roll to gain psionic powers to play the character you want to play. What is the benefit of this randomness?
Second, if a psion class is offered and you want psionics, play the psion. If you allow MCing, take a couple levels if you just want a bit. I would not want them as feats because feats are optional, for one thing (although 90% of tables use them IME...) but more importantly because they are few and fare between and compete with ASI, which are important as well.
We ran into this on another forum, and it is honestly a bit tricky.
Someone was trying to convert Wild Talent into something PCs gained at first level, instead of being of feat. They even had a relatively clever way to balance the dice, by having the skill die portion only apply to skills you picked, which cost you the proficiency in that skill from your class or background.
However, they originally left the damage substitution alone, and this runs a big risk. Taking this option means you have the option for more powerful abilities later, it gives you a powerful ability now, and it gives you a neutral ability. It is purely a buff.
So what do you give the player who doesn't take it?
However, a much easier, and more common houserule, is simply to give everyone a feat/ASI at 1st level. Which I think is the better path, because then it is more easily balanced rather than 1) Are you feeling lucky enough to be more powerful or 2) Well, Bob just chose to be stronger than everyone.