Alan,

A nice rhythm to this. Strong chorus.
Tracks are nicely done.
The vocals are dominating the mix, yes (making the piano seem too-far-back).

This is a forum to Showcase BIAB. So any use of BIAB that "adds to a production" is fair game - even if that is just one instrument.
If using BIAB allows you to add a sax solo or guitar solo or pedal steel or fiddle that you would not otherwise have, then THAT is a reason to have BIAB (which every songwriter/produce OUGHT to have!) and a reason to Show-It-Off in the Showcase.
Go for it.

fj