I don't think there will be a problem changing FTO. Your training records will need to be sent to your new school so that do the required number of hours and also so that it can be shown that you have don the whole course.
I knew a guy who changed FTO mid-way during his IR training. The only thing was a bit of delay in sending his records to the the new FTO
What wrong with your current FTO? ... and go on, tell us who it is!