On first sight Moi3D isn't really made for parametric designs - which is ok.
But on second sight it has everything on board to make parametric designs that even go beyond what most other parametric UI-driven tools can do - via scripting and the node editor!
Same thing with Rhino - Making Grashopper and Rhino-Python first class citizens were imho two of the most impactful features in V7.

Would such a step also make sense for Moi3d V5? I mean, both a scripting interface and a node editor already exist. They are currently just not very documented in the case of scripting and/or separate hobby-maintained plugins in the case of the node editor. Making them an integral part of Moi3D, moving them in the spotlight and providing a way for the community to exchange their modules and templates could be a BIG thing for the new version here also!

Is Moi3D internally generating scripts for all UI user interactions already? If yes, it might be great to provide this script representation - so one could copy out the auto generated "macro" and just replace some of the constants with parameters. An approach that could also be interesting for people without much programming experience to make parametric models in Moi3D.

And further down the line, perhaps it might also make sense to think about a convenience layer on top of the current scripting api - like e.g. build123d is a layer on top of the OCP wrapper around OpenCascade that mainly makes it much more comfortable to use. (On the other hand keeping a 1:1 mapping between UI interactions and scripting would also have it's merrit, so one can even "round-trip" between UI and code to some degree.)
But as a first step just making what already exists more visible and polished could be a big thing!

Edit: Just came across the amazing extension of the node-editor by nkallen that allows to auto-generate nodes when constructing in the UI and vice versa to change the parameterization of the nodes and regenerate the geometry. This is really impressive! Having this in the main application would be really great!
Perhaps even some mapping between node editor schemas and scripts - so one could edit a larger node schema in a text editor and auto-layout it in the node editor again for people who prefer the graphical representation. Full UI<->node editor<->scripting roundtrip!