That's a cool concept
Just a thought (?)
Someone needs to get a good 3d printer
you can use for metal printing products
& make a couple of the tops,
look like org. ribbed chromed or wood grain stickers
but with a cup holder (or 2 cupholders) endless options,
forward part or the door
so it can stay closed & have a recess for a cup holder
probably sell for more than $100 too, IMO look better
that one does the job
but;
I don't/wouldn't like the have to leave the top open as mentioned above
use a limiting strap so it doesn't bare all the weight/overcenter maybe
I have some deal from the 80's
a rubberized weighted like deal with rubber base,
holds beer, sodas (small or tall) coffee cups (big or small) or a big gulp
if you like, has like wire spring-loaded sort of bars in it for all sizes
has an optional rubberized flaps, not shown it sits on whatever surface
seat or the trans tunnel etc.,
if you don't have a console
works quite well
It was like $5.99 at Chuckers/Schucks, Kragens or Grand Auto type place, 40 years ago IIRC
dirty ol' cup holder