I too have been advocating of this and I've used the same technique for years, I haven't found any downside to this approach so far.
"a solution where you can either add PEM's and such to a sheet metal part or have the conversion from part to assembly be transparent to a user."
This would be great but I can see how it would be very difficult for any software to accomplish this.
Sometimes the simplest solution is the way to go. "create sheet-metal assemblies" even though in the current design there are no assembly components other than the base sheet-metal part. At least the option to add them is there and you won't have to redo your drawing's or try to replace a sheet-metal part with a sheet-metal assembly when you later need to add "PEM's" or other press in hardware to a sheet-metal part.
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