I think 1x9, 1x10, or 1x11 are all reasonable options.
On recent tours I found that I am fine with a similar range of gears with my 2x7 (ultracompact double and not very wide range cassette). If building from scratch I'd consider a 1Xwhatever.
I find that cross chaining is more of a problem with multiple rings when the chain is on one ring and rubs another or the front cage. I don't see it being a big issue for a properly set up 1Xwhatever. Do as nun said regarding chain line and it should not be a big issue.