Changing my approach to supplying a full-fledged skin as opposed to trying to tweak lightgray at runtime. Because of difficulty of 'undoing' some lightgray css values like font-family, it seems easier to just fork it and tweak it for my needs e.g. by leaving out any definition of font-family at all so that the client can specify one as a default for the whole document.
Tweaks to match our previous stylistic changes from TinyMCE3.
We don't want fonts explicitly specified in our skin.
We don't need keyboard shortcuts for our deployment.