Problem here is that guys like Sportiello are already at the same level as Onana, maybe higher, and they won't be easy to bring over if the idea is that they'll be last resort options. They can find similar deals at clubs with similar ambitions and potentially a secure starting spot at that.
Our alternative is Dragowski but he won't come since Onana is arriving. We're going to Padelli territory. Someone like Luigi Sepe is the best we can do if Handanovic leaves, unless we decide to overpay for the 2nd GK spot.
Handanovic makes 3.2m, we're offering him 1.5m now. Onana's deal is 3m. There's no way the backup will earn 1.5m, it'll be probably a little north half of that.
The idea is not bad, but Onana does not have what it takes to be the guy who we can lean on for the next years. We need a top 10 GK, not someone who hasn't played and isn't considered the first choice at his club either anymore.