If the Visc 18 Disc has disc brakes, it would save you the headache of replacing worn rims that use rim brakes. The 20" rims wear out much faster than larger wheels since you're doing more revolutions for the same distance.
It has a braze on if it has a double chainring, which saves you the trouble of trying to get third party braze on adapters to work. The only problem with the braze on that's already attached is that if you decide to use very small chainrings, like 44 or 46T, the braze on might not allow the FD to drop low enough. But you'll have to experiment.