I think RHMT could work as an acoustic song, too. The range would be significantly simpler for Bono to work with, and it'd be a great treat for the die-hards.
I think a cover once in a while is a nice thing, especially when it's one that hasn't been played by the band for years. I nearly peed myself when I saw them play "Knockin' on Heaven's Door" in Baltimore. That was three years ago tomorrow. WOW.
I think an acoustic where the streets have no name would sound cool, i saw a tribute U2 band (elevation) in chicago during the summer and they played WTSHNN acoustic and was cool, but its never better than the real thing