This is completely hacky and merely the first way that I dug-out which could keep most of the regolith/gnome stuff to manage the system, but replace i3 with bspwm.
Of course, dotfiles and config are still required.
Replace this line
https://github.com/regolith-linux/regolith-session/blob/main/usr/bin/regolith-session-init#L21
with
bspwm