It sounds like you have the room for the bows ,this is good. First thing I would do is try a dry run of the bows without the headliner. Of course they need to be marked for location front to rear so they don't get confused during this shuffling around. If they can all be installed you should be able to install a factory style headliner. If not. I believe your thoughts of installing a panel board headliner will work but be challenging.
First you would have to cut to size the main panel to fit. Once happy with that out it comes again and curtains so to speak will have to be attached to the perimeter edge. When
the hard panel is fastened to the car you can pull these curtains down to the steel edge where the original headliner is attached and fasten in the same way as was factory intended.
I hope this makes sense. This is described in a simplified most basic way here.
If you wanted to get a better description pm me for a phone #. I would be happy to
help with material choices and more detailed methods to end with professional results. I have a upholstery shop and have been doing this kind of work for over 35 years.
Their is always a way, but it is not always easy.