That doesn’t look like a useful addition. The user still has to understand the edge case and know when to apply empty manually, but the cost of learning new syntax for it is not amortised, since it offers nothing over saying undef; explicitly.

For the case of br and hr, the better solution would be to declare them as empty elements. (Then you could also warn/die if the user accidentally does call text or an element constructor.)

Of course that still won’t help when the user wants the occasional empty td. I see no way to handle that without manual intervention, though, so there might as well be no magic for it at all. Magic must be transparent to earn the name; if it’s not, it just adds extra cost.

Makeshifts last the longest.