I do not have the luxury of traveling light so I pull my Bushtec trailer. You might check out www.aerostich.com. they have some pretty good light touring stuff.
I use the Kriega dry bag system for motorcycles. The US20 and US30. Configure them any way you like as they make different sizes. Easy on and off. Best bag I've ever owne an used and totally waterproof, no messing around with rain covers.
I should mention they come with their own mounting system, no need to purchase anything else.
Rock solid bags!
I don't think you're thinking about this the right way. I love my bike stripped for around town and showing off but on a tour, there's nothing more beautiful than a decked out touring bike set up for all the possibilities. I actually get just as many admirers when she's dressed out then when she's stripped.
I like my Roadster permanently set up with lockable topcase & hard bags.
But if you like naked, I would get this bag & figure out how to fit all my necessities in it and strap it on the pillion seat (or rear fender-whatever u have behind the rider seat).