re: Post workout smoothie meAl Replacements

Cut the crap and stop trying to make it taste good. Everything you are adding for taste is sugar.

If you want to gain/maintain muscle, you need protein. No way around it. Protein shakes are great post workout, but not meal replacement. They are liquid based which means your body will break it down much faster. You need to be replacing meals with lean meat.
Chicken, pork, fish. Want a snack, eat a can of tuna. Want a meal, eat a chicken breast. Add some greens in there too, they are good for you.