I don't outright reject this, but to be honest, I'm not sure that I comprehend what you want out of this request. You can already make mazes of any number of screens, that deposit the player into a boundary that is more then one screen in size, using basic side warps, so...how do you want this to work, exactly?
For the moment, we haven't been discussing adding any new hardcoded engine things, be they items, npcs, or the like. If we did add internal NPCs, they'd need to work differently, and we'd need to change them to some kind of class, or add to the npc class used for enemies. That might be the best solution, to add an 'enemy type' of 'speaking npc', that has some kind of hardcoded path style movement, that doesn;t damage Link, but will allow speaking with a button press. That press would need to be its own variable, as well, to allow people to modify it.
It may be possible to add turn combos, that cause an npc to change directions, that affect any npc object, including enemies to control movement.
I'm not sure how ffcs being modified by secrets would work, but I think it would require some heavy rewriting of the ffc object type. We want to add solidity variables to ffcs, and possibly some memory management so that they don't eat up RAM constantly, so I suppose we could look into that; however, I do not know what kind of control events you'd want, or how you would want to implement them.
Many of the changes that we plan, are toward shifting to using ZScript more readily, and possibly by default for some things. That doesn't mean that we will force people to use scripting, but it may mean that (at least initially), many of the things that we add will be script-mandatory, until we can figure out what kind of interface to use to manipulate them with the editor.
The non-enemy npc type seems to be something feasible though. Instead of attacks, it would have a movement value, and probably a string value. We might be able to do that in one of the next few releases.