My understanding is that your A320 MPL would be valid at other airlines. BA were happy to take EZY cadets with 500hrs and an MPL. Also if you get a new job flying a different type AFAIA you can just put a new type rating on your existing MPL. I don't think they are as restrictive as people make out.
However, if you wanted to flight instruct on SEPs then obviously you'd need to do some hours building as you haven't got a PPL, CPL etc and your MPL is a multi-crew licence only. Happy to stand corrected but I think that's about right.