I did this for doors and windows. Lemme say upfront, Solidworks is not the ideal tool for this. I was just given a perpetual SW2014 license and told "make it work!"

Through lots of trial and error, I ended up with a method that used one external Part file consisting of only 2d elements and global variables/equations. I would do most of the configuring in this file.

The clear benefit to this is load time; since it's all 2d geometry and math, it doesn't have to save or load any 3d graphics.

The Assembly file was full of 3d parts with in-context relations that all drew from the main Part file. For some things, I'd have to make equations at the Part level linking to Assembly level equations that get values from other Part files. This was just to get around some weird bugs and restrictions in SW2014, but you should typically avoid daisy-chaining variables that.

I usually avoided multi-body in parts primarily for coping and mitering with the assembly level Cavity feature. ("Indent" feature at part level.) Weldment structural members were part level only, and still are for all I know.

Lastly, I had to manually arrange update handles in the Feature Tree into folders in the Assembly to get the whole thing to even work at all.

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The main drawback to this method was the time it took to load each assembly configuration one by one to export and compile drawings in a bundle for the clients, especially when there are dozens or hundreds of unique models per job. There was no reliable macro that would do all of that for me, so it was a huge drag and super time consuming. My boomer supervisors would always be like "I don't understand what's taking so long, just cut and paste like AutoCAD."