Another good one would be some alternative to having to de-register the default unit frames. I'm not convinced that the act of doing this is not causing some tainting problems for a lot of mods.
Ideally, the default frames would not actually load if an addon declares itself as a unit frame mod. Like your player unit frame OnLoad does this:
Code:
UnitFrameRegister("player")
Then target frame does
Code:
UnitFrameRegister("target")
And so on. Then the default "PlayerFrame", "TargetFrame" and such would not be loaded or setup.
Any that are not already handled when PLAYER_ENTERING_WORLD occurs can then be loaded and shown.
Not only would this remove some of the ambiguity from what we're allowed to do and touch, but would also save sizable system resources, which is a large factor in many things.