At the moment the number of custom QML types is limited to 50. This limit is arbitrary and far too small for any serious QML development. E.g. I'm currently working on a project where I have more than 60 custom Python QML types, and the project is still under development and growing.

See: http://code.qt.io/cgit/pyside/pyside-setup.git/tree/sources/pyside2/PySide2/QtQml/pysideqmlregistertype.cpp#n59

I suggest fixing the core problem of not being able to create QML types at runtime. Someone already attempted to do this: https://github.com/msorvig/qt-quick-bindings/blob/master/0001-WIP-Support-run-time-QML-type-creation.patch