I did this just to get a feel for how the game runs Bloody Palace files, using Nero's theatre from Fate/Extella as a test, then trying it out with an idea I had.
Main files are packed so that you can install using Fluffy and play around in the stage. Project files are included in the optional files section.

I'm still messing around with the gladiator arena idea with different models......might get it working, might not, who knows?

This "mod" uses vain's DMC4 BP mod as the foundation. For details:

Colosseum
I've fiddled around with the sm1596_battlefloor_mat.mdf2, so that it loads 3 sets of custom textures instead of just one set in the battlefloor folder (ignore the "Owie_albm/nrmr.tex", it will either do that weird texture blending sorcery or won't load with the others. Don't delete them either unless if you know how to edit the mdf, since you'll just get infinite loading). The 3 sets of custom textures (Arena, Arena2, Stage) should load onto the submeshes without blending it with the other textures, so you can use this "mod" to make a BP stage with custom models without getting headaches trying to fix the textures.

Fate/Extella theatre
Uses the original mdf from vain's mod (unaltered). Also, it was originally like 8 meshes, but I've merged them to a single object and squeezed all the UVs together, so it only runs on a single set of textures (the Stage one). I'm not really good with weeb models, so I'm putting this up here in case the anime modders are interested in making a stylized BP mod with it. Just remember that if you want to use more submeshes, you will need to use the sm1596_battlefloor_mat.mdf2 from the Colosseum version.

Potential issues you will encounter if you just decide to use the mod for fun (these are just guesses)

• Invisible stage as you get closer to stage 101
• Weird lighting or reflections
  

Credits

• Rome: Gladiator Arena by Jody_Hong
• DMC4 BP Stage mod by vainluss1
• SSPD077 for the Fate/Extella model