Speaking of Lionel Ritchie...how about the Commodores "Easy Like Sunday Morning"?!!!
Seriously, they should probably cover a Bob Marley & Wailers song (Get Up, Stand Up...Lively Up yourself, etc.) and forget about trying to reinterpret a '70's disco classic such as Love Train. I also love LOVE TRAIN, but only the original by the OJays...the Stones added nothing to it, and actually tainted the vibe of the original.
Someone mentioned Beatles?
Yer Blues would be the perfect choice, a song that Keith actually praised as "quintessential rock music" and played bass on alongside John Lennon for the Rock.N.Roll Circus special.