can anyone give me some advice about giving this editor plus support? Like I said I wish I had built on top of that in the first place, but at this stage, the biggest question is whether I should try to import editor plus features into this, or do it the other way around.
Oh oh! Theoretically you could use http://mossmouth.com/forums/index.php?topic=2920.0
to speed up finding and adding the editor plus differences. Though you're probably mostly talking about adding the new items and stuff to the editor, and it's been a bit too long for me to be helpful on that without freetime to read through the code on my part.
Hopefully that SVN tool is useful. Here's some of my thoughts on doing it the hard way
Saving/loading sprites from GM (.gmspr) is stupid because it doesn't save the collision mask or origin settings when you load it. Maybe one of the custom IDEs (Parakeet is one of them) for GM would have useful features that would help?
Aside from getting the unique objects/sprites in, there's a lot of added bits in existing objects. Right now i'm adding the Ed+ vending machines to YASM and there was stuff for those in almost every 'create' event for every object that is sellable. Trying to save some time by making a script to handle it.
The process for me was a lot of copy/paste and tabbing between two GM windows, and a file comparer for checking code (WinMerge or Notepad++).
I'm tempted to say import your stuff into Ed+ but I don't know how much was involved in your changes.
YASM was already a mess when I started adding Ed+ stuff, and it mostly works. You're likely more capable than me, so there's some encouragement.