I am a structural engineer myself, trust me when I say there are ways to do this. You could place the cycle lane in the middle and simply have it sheltered by the traffic either side, the bridge itself creates sufficient turbulence that you wouldn't feel that strong lateral blow. Anyway, there are examples of longer bridges with cycle lanes (Golden Gate bridge), it is a matter of cost as you say, but once you're doing a bridge anyway, factoring in the cycle lane is negligible as additional cost (plus the current cycle lane takes you almost to the bridge anyway). Also, if you compare it to running a 24/7 shuttle service for 100/150y (design life span of the bridge), you probably break even (not accounting for the carbon footprint of the van going back and forth, often empty for one leg of the journey)
I am a structural engineer myself, trust me when I say there are ways to do this. You could place the cycle lane in the middle and simply have it sheltered by the traffic either side, the bridge itself creates sufficient turbulence that you wouldn't feel that strong lateral blow. Anyway, there are examples of longer bridges with cycle lanes (Golden Gate bridge), it is a matter of cost as you say, but once you're doing a bridge anyway, factoring in the cycle lane is negligible as additional cost (plus the current cycle lane takes you almost to the bridge anyway). Also, if you compare it to running a 24/7 shuttle service for 100/150y (design life span of the bridge), you probably break even (not accounting for the carbon footprint of the van going back and forth, often empty for one leg of the journey)