It's interesting, and I'd like to see it edited together, but my gut instinct is that Luke's not that far gone. Perhaps if some of his lines are cut - namely his repeated insistence that he won't attack Vader - it would work.

But in my experience some ideas that seem guaranteed to work don't and vice versa, so like I said, until we see the scene in motion we won't really know.

It's interesting that you view the Luke/Vader cockpit scene as Luke cracking up. Must admit, that's not my reading of it. For me he's scared of becoming Vader, but I wouldn't say he's becoming mentally unstable. It's cool that you see it differently, but maybe that's why I'm less on board for Luke attacking Vader without a trigger.