That was a whole lot of Bossa indeed.
I'm just a home recording song writer like everyone else - being a retiree probably gives me more time to muse though.
My 1st thought was about the bass being a little to the side. It works but isn't entirely balanced by the acoustic on the other side.
Having bass & bass drum up the middle is no longer essential as we aren't trying to keep the stylus from jumping out of the grooves but it's a convention of the "stereo image" that is imprinted in my mind.
Putting the two bass instruments up the middle does mean a little EQ carving of the frequencies they overlap in - one has to have the meat in that sandwich. At present the bass dominates and the kick drum is subordinate.
The nylon string guitar solo didn't grab me - melodically or tonally. It may benefit from a little more presence but I think it's just my expectation that it'd pick up some of the melody that is the problem.
In terms of your arrangement I see the reasoning and to change it to a more conventional image you'd need to add another guitar or something else which would probably clutter things.
The hard panned vocals are very much of the era of 60s pop bossanova so there's nothing to comment on there.
The whole package is eurobossonova poptastic - the sort of thing I'd expect to hear in an Italian or Spanish movie - all that's missing is the high gloss lipstick female vocal on one side. To put it into a simile to match your style: as light & frothy as the top of a cappuccino with good espresso underneath.

Cheers
rayc
"What's so funny about peace, love & understanding?" - N.Lowe