My original point is that you don't have to check the Hero flag, you can use control groups for that functionality. This is mainly to avoid conflicting with commonly used hotkeys. And I'm just speaking from what I've seen, but people don't typically click the hero button.
What the campaigns and co-op do, and what I'd suggest to do, in lieu of checking the Hero flag in HotS and LotV is making a hero frame in the top left with a status bar and icon.
Alternatively, since that can get cluttered if you control a lot of heroes at once, you can create a dialog somewhere with buttons that select your heroes, since that won't change the hotkeys.
Hero hotkeys are nice, but I wouldn't use any function keys other than F3 since some people use them already. F4 pans and cycles the camera to each of the player's town halls, which is useful for things like larva injects.