If those cost you the money - why are you then locking the editing capabilities of the editor?
Why not instead limit access to the features that cost money to keep running instead?
Use local preview- like in construct2 for the standalone version of the editor and let people export to html5 only if their subscription ran out.
Nw.js is free right?
I had mentioned that way back on page 8 of this thread: pay once to use the software and get all exports for a year, then pay/rent/subscribe to use the export services scirra offers.. You can create/edit/preview a game, but after a year you have to pay to export it. That would still fund the main reason scirra is offering this new technology, and people can still use the software even if their subscription lapses..
Look at the Sibelius purchase plan, it has 3 options (buy, yearly rental, monthly rental):
http://www.avid.com/~/media/avid/files/ ... 0331131511