Version restrictions are very strict.

Backstage has many very strict dependencies in its gemfile, for example, backstage depends on thor 0.14.6 exactly. This makes it very difficult to use backstage with any reasonably sized app.

[bbrowning]

Backstage is not meant to be used inside your application; it deploys as its own application. So, the versions backstage uses shouldn't impact the versions of gems your application can use.