Well, I'm not sure "so be it" is applicable. I'd bet that mechanics during stage races are pretty busy already. The extra workload of dealing with disk brakes makes it harder/more expensive for manufacturers to push disk brakes on a team. A large, well-supported team might very well have to add another mechanic for stage races, for example. If the disk-brake-pushing manufacturer won't pay for that, such a team would have a substantial incentive to use another manufacturer's equipment.

The only manufacturer I can see who'd even have a prayer of pulling off a "You must use our disk brakes" ultimatum to any pro team would be Shimano. And I don't see what the upside is for Shimano in such a move, while I can see the downside for them of teams moving to SRAM or even Campy.

If SRAM, Campy, or a frame or wheel manufacturer as a sponsor tried to force disk brakes on a team without providing substantial financial inducements, the team's response is likely to include several four-letter imperatives. (Does any team at the top pro levels even use SRAM or Campy any more?)

And that's assuming the logistical issues Merlin brought up can be solved (not likely....), or the design changes you mention to make alignment more precise are not only implemented but also consistent enough that wheel changes are actually feasible.

In short, for road racing teams I think disk brakes would be an expensive pain in the ass.