The Heist ending IMO isn't "Dumb" in the sense V learned nothing, it just feels like they're setting something up that may never pay off.
They strongly imply that V is not getting paid in Eddies but something else, what that something else is, is left a mystery, my best guess something that could potentially cure them, or at least extend their life significantly giving them more time to find a permanent solution, that is really the only thing that makes sense, and based on the history of Mr Blue Eyes and his shadow organization (The little bit we know) experiments with the human mind and consciousness, it's very possible they have something to offer. And maybe V is just desperate enough or crazy enough to risk it if they think there is a cure, even if it's against their better judgment.
The problem with the ending is, because it's open, and mostly just vague implications it could go anywhere and mean anything and there is a very real possibility that we never see the result so it will stay unanswered. So, it's not a "Bad ending" it just may be a lot of hope and questions that never pay off.
My favorite ending is leaving with Panam, Either Male V or Female V, in both cases you get to leave the city with someone you love (Assuming you romance Judy or Panam), maybe they find a cure maybe they don't, but they seem at peace and happy and this feels like the most "Complete Ending" the most logical arc for V to take at least in my opinion. Siding with Hanako seems like a safe bet to get help but knowing how it ends is anyone surprised dealing with a Corp didn't work out for the best?
As for V in the next game, it's been said, but It may be better to Move on to a new character, making one ending cannon to fit the new game will undoubtedly cause disappointment, especially with anyone who does not like the ending they choose, leaving it open lets your ending be your ending, and Night city has plenty of stories to tell that don't need V at the center. Besides V isn't meant to be the "Hero" just one story in night city, a crazy story, a fight for survival, but there are plenty of others.
Having said that, I still think some things may be hinted at as cannon, I've said this in other posts things like people who die in one ending being alive in the new game, or exactly how "Strong" Arasaka is things like that will probably need to be accounted for so sure by process of elimination it may force things into being cannon, but I think V's ultimate fate probably stays vague. Of course, they could just do CP2075 and ignore this game entirely since it hasn't happened yet. Or get really crazy with it and transfer a save in, and depending on your ending V has a different start point in the sequel, maybe even has been cured? and the new story is heavily influenced by the ending, with large branching changes? who knows, it could happen, I doubt it as that would be an insane amount of work both for the writing team and the actual Dev team... But it super early and we haven't even gotten Phantom Liberty yet so anything can happen between now and then.