The one issue I can see is that of schedule. It isn't just a question of
slotting a shuttle to go up there, but also ensuring that the mission occurs
after NASA has completed development of independant inspection/repair capabilities.

Consider that NASA was very lucky that the shuttle was grounded at a time when
the station was symetrically assembled. Had the truss been asymetrical, it
would have posed interesting issue, especially when you consider the CMGs's
fragile health.

With the requirement to launch daytime, this may present interesting
scheduling requirements between ISS and Hubble launches as well as maintenance schedules.

On the other hand, if on can launch hubble during a long period when you can't
go to ISS due to daytime launch requirement, it would not have much impact on
ISS assembly.