Reposing will always break the simulation. There is no way around that.  But, rerunning the simulation will not require entering the Cloth Room again.  In the Pose Room, click 'Animation' on the Taskbar ribbon and the contextual menu, and navigate to 'Recalculate Dynamics'.  Select 'All Cloth' and that will automatically rerun the simulation.  Ensure all the adjustments are performed on the last frame of your animation.

The image below is a render you have seen before but the figure morphed and reposed.  I did not have to re-enter the Cloth Room because this scene has been saved with all the dynamic settings already embedded.  All I did was rerun the animation mentioned above.