I'm not an expert, but:
1. I had MUTAs moved or excused when I was in a long training course.
2. I think your company is only obligated to give you the next available training date. Not sure how that would affect your effective-date.
If you intend to get a retirement out of the Army, DON'T get a bad year.
If you aren't a lifer, then you have to decide if the increased pay of Capt is worth the loss of MUTA pay.