A tacky surface on belts has been tried but it ends up being quite noisy. The belts sticks to the platter and then releases making the belt vibrate. While belt slippage does seem to be an issue it seems that compliance (stretching) is much more important.
We experimented with a variety of materials for the drive capstan and heard surprisingly big differences. But there was no correlation between surface roughness and good sound. However, there is a clear correlation between a belts rigidity and sound, with more rigid belts consistently sounding better.
The 2 mil 1/2" wide mylar tape we use with our belt drive motors is quite rigid. But because of the long length (44+ inches) it stretches much more than we would like. The o-ring on the Verus motor is more compliant than mylar but given there is only 1/8" of it between the motor and platter the net result is a dramatic overall reduction in compliance.