What i would like to see is if there is such a thing as a Givi-like
tail bag that locks into and in place of a rear seat.
so you remove the rear seat. and this hard/lockable
case clicks in just like if it was the rear seat. And it should
be of a capacity of around 21L
Also no bottom on the case so the current under seat area
becomes the bottom of the new case.
I'm not sure I trust that latch to hold a case with all my stuff in it lol. I've had plenty of times where I realized it didn't latch even though I was confident I had a nice solid click when I closed it.
I reackon you'd probably have to Frankenstein one yourself. I doubt something like that would be on the market. As somebody5788 mentioned probably not the most secure mounting point for something with that sort of capacity.