Trying to combine physiotherapy with patching sounds like a parenting nightmare. As the AAO says:
Persuading your child to wear a patch can be a challenge, especially if the vision in the child’s amblyopic eye is very poor and the child is objecting strongly.
They go on to say:
Unfortunately this is an area of treatment where there is no “quick fix” but it is also a brilliant opportunity to spend a great deal of time and enjoy playing with your child.
Unless the physiotherapy is something that is enjoyed by the child, there would need to be a complying reason to combine the two. Medically, there is no compelling reason to combine the therapies, but for individual patients there could be practical reasons (e.g., time)
to answer your question, the visual system does plays a role in balance. The Vestibular Disorders Association has a nice graphic depicting how sensory input affects balance:
While vision plays a role in balance, the blind can compensate for their visual impairment: http://www.afb.org/section.aspx?SectionID=67&TopicID=313&DocumentID=3470