I'd say either your version or the @Salty-Secrets option below (usable vs NPCs only) are your only realistic choices. Rolling generic skills for PvP social is never going to work in a MU environment. We can (and have) argue circles around why it SHOULD work, how people who don't honor dice are bad, awful people, how people who can't pose good social stuff are pathetic RPers, etc, but in the end its just empty sound & fury. It never works, and we know that from experience. That said, I'm not sure powers are in the same category, since they tend to have more defined effects.
Some version of the NPCs-only approach is what many mainstream games embrace (D&D and all its inheritors, Pathfinder, 13th Age, etc) with a pretty self-evident record. They do still have some powers that can control other characters but typically they're very straightforward in the parameters, and where there are glitches in these systems they're usually confined to individual spells/class abilities making it much easier to narrow things down and ban/patch. Otherwise, dice are there to shortcut NPC interactions and work pretty well for that. You can always hand out some bonuses for excellent RP, but the game doesn't hinge on it and it works reasonably well satisfying various player types.