I really like your Mega Armored Nobz. I am intending to get some for myself.
You asked about Boss Conversions, ggreat, there is plenty that you can do.
I like Mega Armor, but find equiping my Warboss with very basic equipment works rather well for me.
I made my Warboss out of an Ogre Kingdoms Ninja Maneater, Mega Armored Power Klaw, and a Classic Nob Head (the one with the Big Iron Gob.) The Model turned out great and is just about the size of a regular boss. Although he is very fat, I chose Badmoon for my fluff and it just adds to his character.
If you wanted to go a bit more ambitious you could have a Warboss Torse sticking out fof a Dreadnaught (Marine or Ork, you pick) pulling levers and things that ultiately represent Mega Armor.