Instead of constantly adding and updating tons of mods, why not add the function for us to design our own parts!
Since after we finish the tech tree all our science is basically sitting there doing nothing, science will be used as the "cost" to design and also to balance.
General idea of how it works would be as follows:
Choose part type (pod/electric charge generators/fuel tanks/drills/grabs/etc)
Choose a basic shape/use existing part as template
Edit the shape, the shape will be shown something like in procedual fairings but can click and drag the line(frame) to tweak shape to liking
Edit the stats like thrust/fuel consumption/kerbal count/storage capacity/generating speed.
For balance, the more OP the custom part is the more science it costs to "make" this part, e.g. high thrust engine with low fuel consumption will cost tons of science whereas just tweaking the shape of a normal pod to look nicer would be very cheap
As for actual $$$ cost, maybe can spend more science to lower cost(by making process more efficient)
The current tech tree can be integrated by say parts cant be made smaller past X size until miniaturization is unlocked or something along those lines
Policies also can be integrated, say if you are focusing on reputation, maybe then pods must provide each kerbal X amount of space rather than say squeeze all the kerbals in a tight pod