Hi,
The most difficult part is the code base of JB products - it's pretty old now comparing with Joomla 4
What does it mean? that Gavick and Shape 5 had an easier code to update? However it seems that they all used the same programming language, at what level Joomlabamboo code would have been more difficult to update?
Anyway, personally an update of Buildr template and Zentools module would be enough at least to begin with.
I'm still confident in a partial update... Thanks - Lorenzo