Proportional, monospaced and metrics keys

I’m working on a project that has a monospaced axis. At the moment these are two separate files. I’d like to have all these masters as one file, but what’s stopping me are metrics keys: the proportional masters have lots of metrics keys while mono of course don’t have any. I can’t think of any simple way to merge the two except adding == to all mono glyphs but that would seem very annoying to work with.
Am I missing a potential solution, or should I just stick to different font files until production?

I would stick the metric keys at the layers (adding ==). A script can do that. A script that keeps them in sync would be handy, too :wink:

Still running into this… So I’ve been thinking what would be the perfect solution would be to create some sort of metrics keys groups. Maybe a master CP “link metrics keys to master” could work?

“==” works well but only for small exceptions, otherwise it becomes very slow to use unless scripted. So this could be a really nice addition?

I don’t see how that CP would help?

So that metrics keys would apply only to certain masters?

I had a similar idea but for italic reasons: CP defining something like “this master is group B of metric keys and kerning groups” and in UI the metric keys/kern groups would be totally independent when you switch to masters of group B. Have metric key n in some masters, g in some others and empty in the rest if you will. Never bothered to suggest because sounds like a lot of work and you can work in two files or add ==.