I think you will find that NJME don't have any 400XP. Just 750/800XP, Falcon 2000 and G450. Anyway, I think they have previously hired non-typerated folks.
With regards to the cadet program:
Yes, NJE did have one. Most or all cadets ended up joning on the midsize (XLS and Hawker 800XPC) I think. The intention was to put them on light jets, but there was no requirement for additional crew on those jets when the cadets startded to come online.
Once online I think they are subject to the same rules as everybody else with regards to fleet changes and upgrades (seniority and seat locks).
They will likely stay on their mid-size (or small cabin) fleet until they have 3000 hours which should take at least 6 years or more. Their first command will be on a light or midsize. A large cabin command is many (10+) years into the future for any of them.