Building a single bubble app with a team, Impossible? Solutions/Hacks/Ideas/Experience?

Have you tried working on two apps and just linking the databases together? That should help. Especially since you have 100+ pages. I think that is what I would do if need be. Try to separate parts of the app into 2 apps. You can always link back and forth between the two fairly easily with links as well. Then more easily you can have 2 developers at the same time.

You can add one of them as, for example, app.domain.com for one of them. Share the same main domain.

Just for reference, this is what I would do.