Running with both PGTK and an X toolkit?

[Spencer Baugh]

I'd like to configure an Emacs with both PGTK (for Wayland and Broadway)
and an X toolkit (for X - probably Lucid).  The reason is that I'd like
to simultaneously have X frames open and Wayland/Broadway frames open.

(More specifically, I think it would be cool to be able to use Broadway
to connect to my Emacs remotely through a web browser, but I use X for
my normal Emacs setup.)

Is it possible to have both PGTK and an X toolkit configured into Emacs?
I'm willing to do development work to make this work, if it's not
categorically impossible.

And if that is possible, is it possible to have two frames using two
different windowing systems at the same time?  (I feel like I've heard
about people doing that before, at least for other combinations)