I didn’t know that map envy even existed but I think it is a good thing for pushing development of new things.
I searched a bit for plots made with Caraïbes and actually found one:
It even sports that kind of elegant frame. Not as elegant as GMT in font reproduction and line width but the idea is definitely there. They went the easy route on the corners, though.
Do you think that would be nice addition to GMT to have/implement, @Joaquim?