I need ideas for the simplest way to add new Feed options.
Depends on what your idea of "simple" is.
Is there a way to add a Feed option to say dialogue? And have it a Persuasion chance/check that then equates to a Feed success that resets the FeedTimer?
Or is there a way to make the Feed Perk work say on a Paralyzed enemy or just any enemy that is prone or perhaps even an enemy that is dead.
You can do either one of those things you ask about here, but the problem with the first one (dialogue) is that the only feed animation in the game is made to run on a prone actor. You would have to call the VampireFeed() function from the PlayerVampireQuestScript using a fragment from dialogue. But then it will look really bizarre, you trying to feed on somebody who is standing - and most likely - moving around after dialogue ends. Although you could set them unconscious through the same script... but since that doesn't cause them to fall over, you still look funny running the animation. Unless you don't care about the animation, in which case just leave off the StartVampire call (which starts the animation... if I recall the function correctly).
Changing the perk is relatively easy. You can just add/remove conditions in the "Target" section. If you want to feed on the dead, just remove the IsDead==1 condition. If you wanted to allow feeding on paralyzed victims (I was thinking about adding that to my mod too), you can maybe add a HasSpell Paralysis==1 or something like that (don't know if there's a "paralyzed" option for conditions).