I personally would be interested in doing one of those down there, sounds great and I like a change of scenery.
Anything much past Portland and I'd probably be looking to lodge somewhere at least one night. One idea around that would be to have a wine country loop that starts and ends at an "official" hotel where everyone stays and can continue the "alcohol testing" into the night. Just an idea, everyone doing their own thing works too.
I probably wouldn't be able to justify going down until Spring, what with the two drives already this fall and then the holidays, etc.
Looking forward, even with the "official club" aspect kinda going away, it seems like the local SVX owners are still settled into somewhat of an annual meet schedule:
January - March: Dinner get together to hang out, maintenance meet at Earl's house (could be two seperate events or combined in the same day).
August: Dabob Seafood Fest
August/September: SWWA/NWOR Driving Tour
October: Fall Colors Driving Tour
So you can see there is a pretty big hole between winter and late summer, even more so when considering that the only actual DRIVING events are the 2 that take place in the 2nd half of the year.
Of course this is all from my perspective being pretty far north of your proposed routes. There's a good crew closer to you that may be open to doing this much sooner.