honestly, some of those big GS Beemers are probably heavier than a cb honda will ever be. The question is how useful do you want the bike to be? The clutch is the only real issue, and honestly the lighter you can make it the less of an issue.
that being said the only thing "CB550" that will be left at the end of the day is the engine and the frame. Maybe a gauge. that's it. For the money you are going to put in you could easily buy a used DR650 or a KLR.
Figure out what you are actually going to use the bike for and then you can tailor your parts choices to the need of the bike. For instance, I have an Ironhead sportster that I wanted to use as a vacation/surf runabout. I knew I wasn't climbing a mountain or doing the TAT with it, but I was going to ride fire roads, beach roads, stuff with lots of sand and ruts, mostly with a surf rack and board. So I selected a mix of flat track and hill climber parts and used the old XLR factory race bikes (cross country trials and hillclimb) as a pattern. The end result is more like a stock dodge durango than lifted wrangler on 33" super swampers, but it fits the need and it didn't cost me a fortune. Plus I get lots of strange looks. would I bash about on a 20 mile off road trail? eh...maybe but I am nuts and I would expect the bike would be a write off at the end.