I just read your draft proposal @Suraj and this discussion here, very interesting!
My opinion: your definition of the problem to solve is very good: Designing reinforcing bars in FreeCAD is currently slow and requires many steps. It should be automated into some simpler, "all-in-one" operations. However, I have the impression that your proposed UI mockups don't really address this. They seem to me not very different, in terms of complexity, than the current ones of the rebar addon...
This is of course the main subject you propose to work on, so there is no need to have it solved right now, before even beginning
But I would suggest, maybe, instead of thinking "ui controls", to think "scenarios". Or in other words, think "wizards". Like, what would a structural engineer want to do? and identify these general tasks that that person would want to perform, ex. "I want to add rebars to a column", or "I want to add rebars to a beam", or to a slab, or "I want to design a completely custom rebar scheme", and study how you could simplify and automate the steps need to perform this task.
This is not necessarily a big change to your current plan, maybe more a question of refining how things are presented to the user, and developing it more like a "story" or wizard. I don't know if what I'm saying is very clear or if it makes sense...
Anyway, this is just an idea, not a requirement of any sort. Keep going!