This got much more of a response than I anticipated.

I know the limitations of Basic Economy and what I'm paying for. My specific concern that is that as a potential result of my (lowly) medallion status I am assigned an economy seat earlier than others in the BE class(which may initially seem like a positive). But as a result I'm never one of the people at the end of the list who ends up getting assigned a comfort plus seat since they ran out of standard economy seats.

So medallion status resulting in an early seat assignment basically insures you don't get a comfort plus seat when booking BE.