Starting at WoR

Your solution will work, but if you want something a little cleaner, I think I have an idea:

First to answer your question... any vanilla savegame in WoR should work as long as you didn't heavily alter the event bits in your game, if you did, then you need to alter the event bits set in the savegame to make sure you haven't messed up the progression of your WoR-only hack.

That being said, You could also redirect the opening event to a new event, written by you, that sets up all the necessary WoB event bits to ensure nothing is blocked off or WoB events that may play in WoR if not set... then jump to the opening of the WoR. Then any new game will jump right into it and the game and saving should work just fine from there. Then you wouldn't need a save file for everytime you wanted to start over (like everyone here doesn't have 150 million save files laying around anyway... but still).

This sounds like a really interesting project, keep at it.