Is it acceptable to forgo shoulder treatments when using sleeves with the M.A. bodice pattern?
You can for go Shoulder Treatments. But in my honest opinion, Bodices look much better when there are shoulder treatments of some kind.
Just like Bodices look better with waist treatments as well.
The shoulder treatments are more of a Northern European look. The further south you go, the more likely you are to see gowns without them. Which look you are going for is entirely up to you.
If you are going for Elizabethan then yes, you will usually see some type of shoulder (and waist) treatment. I use the MA bodice pattern as the base for my Florentine gowns and don't use shoulder treatments. To get a better idea of what was or wasn't done- go to the Web Gallery of Art and look at portraits from the time and place you want to represent.