FWIW, I don't own a Downtube folder (yet) but I've seen a bunch of photos.
In one, I noticed a "stand" projecting down from the bottom-bracket shell.
I have a similar stand on my KHS - it keeps the bike upright when folded.
I've seen kickstands advertised online that attach to the same point on a folder - the bolt that keeps the "fold stand" (to invent a term) on the bike.
Perhaps this would work on the Downtube.
_________
On the topic of derailleurs and cassettes, I have a few thoughts.
If an 8-speed derailler and cassette is significantly less expensive than a 9, I'd suggest staying with an 8.
8-speed cassettes give you a range of 11-34T. 9 and 10 don't give you anything but a slightly tighter gear spacing - unless you go Capreo, you're still limited to 11-34T. (not talking about internally geared hubs here - just deraillers)
*shrug* My 2 cents!