Joined: Jul 2002
Posts: 40,863
Likes: 3,115
From: Sacramento, California, USA
Bikes: Specialized Tarmac, Canyon Exceed, Specialized Transition, Ellsworth Roots, Ridley Excalibur
Chain length, or rather capacity to take up chain in the two smaller rings would be an issue. Since you'd still have to have a RD or chain tensioner to accomplish that, it would be much simpler to go 1x3.
Actually, now that I think this through a little, it would be really simple and easy to keep the 8, 9, or 10 speeds in back. Lots of CX bikes do this.