So far I really like the PART_PARAM:SID=ASM_PARAM method. It works well so far, I actually have 10 parts in an assembly using 3 different parameters. It was a little less then I originally said, BUT I am still going to make 6 copies of this assembly when I get this one finished. And then change all of them.
I only have one main assembly and this started in mold package, so the pieces are extracted (most of them).
Also, once this is finished there is a slim chance it will ever get used again.
I know what you are saying though, like some things Pro, sometimes stuff just seems to die on it's own.