Pop bumpers on an elevated/overlay playfield seems like a nightmare in general, maintenance would be a big pain. I can't think of a machine that has a pop like that, but my internal pinball database is getting pretty dusty.

You might be able to make the kickback lane work with a subway or maybe make the machine a widebody and go around the mess?

Assuming that it's about moving the ball unseen (which makes it much easier) from the sink hole higher on the table to the apparent ejection hole and kicker low on the table.

One could have the ball go quite low below the table surface and then use some kind of mechanical kicker to get it up to table level again near the bottom. It's possibly a unique problem, but seems to be much less work than building the rest of the table.

Just put one pop bumper there, you could make it work

Hm what's the problem with that? I understand that the bumper extends down, but what else needs to be on the underside that makes this unbuildable?