Most of these are on the maybeboard already:Alright, let me try a few more...
Winding Constrictor (bad with Persist, but great with the other stuff)
Vizier of Remedies (wannabe Melira)
Hapatra, Vizier of Poisons (Persist-based loops turn into token-making engines)
Sun Titan (general value there)
Spike Weaver (fog whenever you need to)
Vish Kal, Blood Arbiter (not a cheap spell to cast, but I've gotten a lot of mileage out of it)
Requiem Angel (haven't tried it myself, but I've seen others have success with this)
Winding Constrictor - Have it. As you said, it messes up Persist, and might cause a combo piece to die, as its ability isn't optional.
Vizier of Remedies - Have it, and it's due to go in Combo. It can negate the Persist cost which is all I need.
Hapatra - Have this one too. Can combo for infinite creatures.
Sun Titan - Have one, awesome utility. Might find a place.
Spike Weaver - Hadn't seen this card before. Potentially useful utility.
Vish Kal - Have it. High CMC, but it can sac as an instant and combo destroy creatures, so it might find a place.
Requiem Angel - Don't have it. Combo potential, but high CMC.