No, it's not better integrate it directly into the engine:
1. dev time (the number or significant committers can be counted on your thumbs)
2. flexibility (would require configuration support code for draw mode, geometry)
3. once stable, it will be included as a default widget
4. 'basic' enough that the game has been played for years without it?
(the same applies the the SelectionButtons widget, which I'm guessing you
are referring to when you say, "I can't see which units I have selected")
You'll really have to start getting used to the idea that LuaUI will always
be enabled. As it becomes more stable and feature complete, it will be
_the_ GUI for the game. Writing redundant engine code for features which
are easily accomplished with LuaUI is a waste of dev time.
P.S. If you really want it, code it yourself
