Have your guests that complain about the window being off, take their baths outside.

No one is going to take a bath in that room unless the window has some sort of covering on it. Wait until the construction is finished and disguise the imbalance with a window treatment.

You could put a grab bar next to the window to off set the window.

Uninstall the tub. turn it sideways to center it on the window. Add any necessary wall extension. Done.

Put up a shower curtain and stack it open on the wider side.