As I posted on X, the biggest complication with sponsors is that the sponsor transaction can become invalid depending on innocent block reorderings, which would require it to be treated as a coinbase output and mature before it can be used in a normal transaction. I think this prevents sponsorship from being done as a part of regular transaction operations.
That said, sponsors (or other transactions that are provably re-bindable to either a current txo or one of its ancestors) could be allowed to spend before maturation, which means that a dedicated sponsor TXO could be spent repeatedly without maturing between spends, and only a subsequent spend that would not be re-bindable would have to wait for maturity.