I might've confused you mentioning the MG213A, it was just a note in the documents reproduced by Monogram that FW hoped one day they might change the armament of the C-1 from 1x Mk108 and 4xMG151/20 over to 4x MG213A
The C-3 was always going to be just 1x Mk103m and 4x MG151/15 plus bombs/rockets
The C-1 is a zerstörer, the C-3 is a schlachtjägd, but between them they absorbed the roles of the Ta152E recons and Me410 schnellbomber, and always had secondary jabo and jäger roles but Dora-11,12,13,14 and 15 would be doing most of that.
And the whole thing was, during this period of production the Me262 and Gotha jets were supposed to get all sorted and come to the forefront.
The RLM had to know the days of the piston engine warplanes were limited. It's a bit like spending money on an engine rebuild when you know you're buying a new car next year. Already during early 45 the greatest potential for combat successes was the Me262 squadrons like Jv44.