You can convert an mpl to an atpl but restricted to multi pilot ops only. No grandfather cpl spo grandfather rights.
operator restriction is a hoax, as a matter of fact a majority of thr mpl cadets went to other places below 1500h (ASL/Brussels/…) this maybe tells you something about tuibe as employer as well.
50k from zero to hero incl TR, and a contract, good deal, take it. Expect to be treated like a kid in primary school. Be able to deal with ancient attitudes from instructors at times.