I think we should probably try to address this in connection with
another issue: a suitable way for opening a tty: open a frame only
once it is "needed". One problem we currently have is that it is not
really pleasing to specify Emacs frame geometries, colors, toolbar or
menubar presence by using .emacs and/or customize: that way, the
initial frame will first get mapped wrongly, then flicker into
shape/position.
So one would want to have a delayed mapping, basically happening when
sit-for is called.
If this point is never reached, we don't need a mapping at all. In a
similar vein, if emacsclient never reaches a point where it would be
interested in looking at tty input, maybe it is not worth mapping a
frame (and stealing the minibuffer). Of course, the question when to
call "top-level" remains.