The lever would simply be made to swing in both directions just like with the current MTB DCL shifters. The tab area would either have to be larger or you could make two tabs so you could hit it at the lower portion with your fingers and use the thumb on the upper portion. An assist extension could be mounted as an option so that you could press down on it when on the hoods and it would swing the lever outboard. This would give you a thumbshifter ala Campy Ergo. You might even be able to make the upper portion of the tab also a removable part and make different sizes so you could tune the height in accordance with a rider's thumb placement. Different sizes and shapes of the assist extension could also be made to accomodate different rider's thumb lengths so they can actuate the "thumbshifter" from their favourite hand positions.