Actually there might actually be an advantage to mounting the brake forward of the stays aside from the cable routing issue.

One of the functional differences between front and rear brakes is the effect of brake arm flex. On the front the arm flexes upward when stopping, on the rear it's down. The difference becomes significant on rims whose braking surfaces aren't parallel, and flare out toward the outer edge. Flex moving the shoes outward increases brake force as the shoes move to a wider part of the rim, while flexing inward reduces it.

This is one (among many) reason that front brakes tend to have a more positive feel, and if your rims flare outward, you'll feel the improvement.

The only negative issue you might have mounting the brake forward is that the bridge might not have as large a flat mounting surface on the front as it does on the back. Possibly this might make it hard to keep the brake centered, but there are various ways to solve that if it becomes a problem.


BTW- as others mentioned, don't forget to reverse the shoes switching left/right and forward/back.