Thanks for the responses. It looks like no free seat assignments for me on AA in March.
From my AA experience, even regular "premium" seats help on AA because they don't randomly assign these seats to non-elites unless the "regular" coach seats fill up, so you're far more likely to have an open seat next to you if you're booked in those rows. And, right now, there isn't any booze in coach on AA so you're not missing much (a small bit of extra leg room) by not being in MCE.