Nice idea.

Maybe something like this would be more a more secure material for the bridge


I also like the old idea of a Vivarium, with a false floor. i.e two levels.
You would have a normal wood vivarium with glass sliding doors, but a false floor with a bit of pipe leading to the dark underground section.
The pipe was raised a bit so substrate would not fall down the hole to the lower level.
The underground section is in the form a a draw so you can access it.
I used these before I had ball pythons, but i am thinking now, it would suit their underground burrows well.
P.s there was a shelf too in the top section for climbing and additional thermoregulation.