Branding aside, is there any reason the MCU couldn't just call them Avengers, the successors to the original generation?
Of course, they would always be Young Avengers in relation to the OG Avengers, so that could justify the name.
Honestly, they could call them the Champions - but they'd be giving up the Avengers branding, which is probably not something they're willing to do at all (and they haven't exactly set up any particular reason for these kids to want to stay separate from the actual Avengers, unlike in the comics).
They could call them Young Avengers if they came out this year, maybe next year or the year after, but that's clearly not going to happen so Kate at least will be pushing 30 by the time they make something and that will just confuse people.
They could call them New Avengers (or just Avengers or something similar to that), but at that point it just begs the question of why this team? Why only younger characters? If they're just going to throw out the idea of them being the Young Avengers (or the Champions) and actually focusing on that, then why not just take the most popular characters and integrate them into the actual new Avengers alongside Strange, Shang-Chi, She-hulk, etc?
If they're giving up the focus on the younger characters being younger then surely it makes more sense to just have one Avengers franchise and only focus on a more broadly appealing line-up anyway, rather than having a secondary line-up only aimed at people who love the modern/recent characters.
Is Ali under contract? Cast him as Kang.
( I have no idea how movie contracts work)
He'd be under contract for the character of Blade, not for whatever they feel like making him do. That could be negotiated around if they really wanted to, but A) they've already abandoned Kang, that's why they cast RDJ as Doom and B) he went to Marvel to pitch this movie in the first place because he really wanted to be Blade, so he probably wouldn't be amenable to having his contract switched to play some other character.