What is the best way to install multiple versions of a workbench? The problem is all directories are added to Path. Thus there are all modules twice. Something is needed to say from which directory to import.
I don't know which import style you use and there are some differences regarding Py2/Py3. But regardless of all that in the end you likely won't be able to use the same import statement for both modules. One will for example need to have an additional suffix, such as NameDev.py or name_dev.py. This therefore isn't all that much FreeCAD related, this is Python related.