For my language I've been using a US layout with a similar alteration for years as well on Windows and Linux: AltGr+C = Č, and AltGr+V = Ć (the second one is much less common, basically only used for writing names). Similar for Š, Ž and Đ, I stopped bothering with stuff like á because I need them maybe once every couple of years.

My point being: wow, I've never thought about standardizing the layout, what a marvelous thought. Not for the general public perhaps, but for some programmers it would be a godsend. The whole terminal is basically non-ergonomic on other layouts. Stuff like ./ is right together on the US layout. Similar for coding. I preach to my fellow developers and they see my point but most won't go outside of what's provided by the OS for some reason.

I don't know enough about other European languages from my "region" to make a more general standard (though I suspect it wouldn't be as simple as creating a single "eastern" one, I doubt e.g. Hungarian and Polish have so much in common) but it's a good idea, something that could be collaborated on.