So, i was playing the MB this morning and having some fun, it's fast and intuitive, but then i noticed there is no optin to upgrade a monster to Elite or Solo. Am I missing something?
Nope, you are not missing anything. There's currently no way to make an elite or solo creature with WotC's monster builder. I suggest you use Asmor's Monster Maker (Monster Maker - Asmor.com) instead.