I have bought tickets for family.
MCO-EWR RT in coach and then EWR-TLV RT in business. both in UA, of course.
It was so much cheaper than business/first the whole trip that it was worth the hassle.
UA had no problem. checked luggage through and when there was a delay in the MCO-EWR, they protected the passenger on a later flight which left earlier than the original flight without even asking.
One of those days when UA works great.