Especially since I think a pretty large number of computers/hostnames that are ssh'able today will probably have the same root password if they're still connected to the internet 10-20 years from now
Not that this is a bad thing, but first start using keys, then start rotating them regularly and then worry about theoretical future attacks.
A captured SSH session should never be able to decrypted by an adversary regardless of whether it uses passwords or keys, or how weak the password is.
In TinySSH, which also implements the ntru exchange, root is always allowed.
I don't know what the behavior is in Dropbear, but the point is that OpenSSH is not the only implementation.
TinySSH would also enable you to quiet the warning on RHEL 7 or other legacy platforms.