As some may know, I have been trying to achieve this kind of open world gameplay in JJ2 for some time (if not always very actively).

If JJ2+ won't let me do it, I'd gladly write yet another utility that gets in the way as little as possible, specific to your purposes (which would otherwise require scripting).
So what I'm trying to say, don't give up on your project, because one way or another, what you describe is perfectly doable.