I work in web based software development and I'm kind of thinking the best bet would be to create a final stand alone application (using the current web based app/plug-in as a base) that runs on both windows 7/10 and mac OSX up to High Sierra (forget about supporting ipads and iphones, they change every year). The logic being that the Win/Mac app will always work, via a virtual machine if needed, even 10 years from now.
I don't think it would cost too much money to make that happen as the application already exists and could be ported pretty easily. Users would then have a "final" physical app they can download and keep for when the browser version finally ceases to function due to browser updates etc. I understand there are costs involved, but it seems like the only logical solution for supporting the full range of this product and it's hardware moving forward. I'm honestly mostly concerned with the plugin potentially disappearing from chromes database over the next few years, otherwise if it sticks around you could likely use older browser emulation to get the app working.
I just picked a GC up from a sale last weekend, it was sitting in the store for about 5 years, I know because I've been eyeballing it the whole time... picked it up at a silly price tbh.
I doubt EBMM would put resources into creating a standalone app for a platform that is being phased out. A more realistic approach would be for EBMM to publish the GC API so open source folks could put together a community-supported solution.