Have you heard if esri has any plans to change GP toolbox format (.tbx file) to text-based format in future?
The issue is that we can't track changes in binary tbx file using source control system. With text based format it would be easy.
Most of our tools are .NET (COM) based. Some used for printing are Python based. Therefore we use a custom toolbox (.tbx), not Python toolbox (.pyt).
Or alternatively (maybe this would be even better approach) esri can provide a tool buildTbx which takes some text-based toolbox descriptor file, finds what tools should be in toolbox, what are inputs and outputs, also other files needed to be included in toolbox (.py files) and creates that binary tbx file as an output.