I think Sigma Foveon sensors are the technology of the future and it’s only a matter of time until they solve the few remaining issues (like low quality at high ISO). That said a Chinese company promises right now that they can modify your Sigma DP camera in an interchangeable lens camera for every mount. On the picture you see the Leica M-mount version.
Just send in your DP camera at Taobab (translation here) and ask for the mount you want. The full modification costs you round $300.