The psychic provides the different casting mechanics

Oh yes, I see. It has the "lower level spell slots drop off as you gain higher ones" thing that the oracle and magus also have, which is actually pretty similar to how 5e's warlock works. I like that mechanic, but to be clear I'm not suggesting that specifically is what warlocks should have. It's one option, for sure, but my main concern is that despite casting the same types of spells as wizards, the spells be different in some way.

Interestingly, looking at it again the psychic's conscious and unconscious mind being essentially 2 subclass choices reminds me a lot of the 5e warlock's dual-subclass choices in the patron and pact boon. Personally I don't think the pact boon is an essential part of the class (that aspect could just as easily be a feat), but that is an amusing parallel.

The 5e Warlock is just much, much too 5e at this point. Paizo can’t out 5e the Warlock, and as played most Warlock builds will not work in PF2

I mean, I'm not suggesting you just take a 5e warlock and play it in Pathfinder. That would be absurd.

I'm not particularly convinced "it would invite negative comparisons" is a strong argument against anything in Pathfinder. The entire system by its very existence has, since 1e, invited comparison to D&D. The warlock is, to my knowledge, the only class in 5e D&D that doesn't have a direct equivalent in Pathfinder. And that's a shame, because in 5e it was my favourite both mechanically* and thematically.

* something I haven't bothered talking about here at all because fundamentally the reason I like it is because of how much it feels like any Pathfinder class, with Invocations being basically like class feats. Something no other class has.