The easiest example might be someone like Fitzchivalry Farseer, but honestly, an awful lot of "romantic fantasy" (i.e. the "Blue Rose" genre) has "magic" which is basically psionics, rather than vice-versa (i.e. it's all telepathy, empathy, telekinesis, mind-battles and so on, not rituals, fireballs, magic traps and so on).
In general in fantasy literature, a pretty significant proportion of characters who wield "magic" or some kind of supernatural power are using something which in previous editions been "psionics", and which worked in a very different way to D&D's flashy, big-effect-oriented slot magic.
I think the issue is that I come from a fantasy-literature background, and I'm interested in characters who have abilities like that, more than ones with flashy BOOM-spell abilities - those have their charm too but it's a different charm.
Warlocks are cool but they're extremely specific. They can't be reskinned as a psionic caster without both rules revisions and a sort of incredibly elaborate re-skinning. You'd want more in the way of cantrips, completely change out the warlock-ability-things for psionic ones, get rid of the whole mechanical bit to do with the patron, and use that design-room to give you the ability to use some kind of spell-point-based system for low-level spells or something maybe. I don't think it would really work out well.