I think the 57 has a minimum deck penetration of 1.9m if you want anything more than the 120rds in the gun itself. You could get away with an electro-optical director for the 57 seeing as where this operates too me thinks.
I started doing an M113A4 some time ago, I cannot confirm that correctly portrays it 100% accurately though (hence it not being on a template at the moment)
You could make the superstructure sorta hexagonal and have the launchers further towards the edges possibly with the outside of the enclosed launchers being flush with the rest of the hull below it?
1: Added to the to do list 2: Hmm Millennium it is then 3: Could replace Millennium / 40mm with two of the RAM thingies then possibly add auxiliary coverage with MLG-27 or Millenniums somewhere amidships one per side? 4: I share the same thoughts I could extend the bridge structure back as suggested...