My opinion is that Unioniste, despite looking a decent prospect since joining Nicholls, would almost certainly find this a race too far at just 4.
He is related to My Will, though. That would give you hope, although I take your point about maturity.
I can’t deny he looks good and he has shown maturity beyond his years in his only 2 starts thus far, especially with his jumping, but it is the age concern which is the issue for me. He’d have to be seriously good to be winning races of this calibre at this stage of his career, even off such a low weight. Very promising horse though, one to keep an eye on.