+1 to basic remapping. The vim-surround might be trickier; I didn’t see anything preexisting for CodeMirror. But my biggest VIM-grievance right now is I can’t set it to use the System Clipboard. I didn’t see anything out-of-the-box with CodeMirror so it’s likely a bigger ask. But I’d be super grateful!
I use Alfred.app’s clipboard manager very frequently so not using a shared copyboard is pretty frustrating. Worse, I lost a file from a bad cut and paste and no way to restore it.