The role doesn't necessarily need to be covered by a bench hooker but you have to have SOMEONE who can play in the outside backs AND in the forwards. AND you need to have their forward position covered by the bench.
As an example, the Roosters have Connor Watson, named at lock, who can also cover half, centre, hooker and fullback.
The NRL profile of Connor Watson including career statistics, season stats, games, tries, goals, tackles and fantasy scores.
www.roosters.com.au
But you don't really want someone as valuable in the middle as Patty playing some other bandaid position. Hence it makes more sense to have a Mr Fixit on the bench.
You're right, though: we don't have anyone on our roster who can fix our bench other than Oates, and for whatever reason, Kevvie appears loathe to use him. And if Sailor has the defensive liabilities many believe, he's not fit for NRL.
You're also right in that you can get by with 2 specialist hookers BUT someone on the bench needs to be fast enough to play in the backs.
We're in a bit of a pickle because our problem players are Walters, Smoothy and Hetherington. They're all good enough to take the team to a Grand Final in their respective positions but their collective lack of versatility causes knock-on problems. If we try to solve it by replacing them with other players, we might succeed in putting insurance in place, but might weaken the team otherwise.
For a hypothetical solution, let's start with our current hooker rotation, which is eating up two interchanges.
Walters: adequate hooker for a short burst, adequate cover in the halves. Can kick and pass. Not a playmaker. Too slow to play wider.
Smoothy: slightly better hooker for longer periods. Can kick and pass. Not a playmaker. Can play a middle defensive role. Too slow to play wider.
If a half goes down, Walters moves into the halves, Smoothy stays at dummy half. It works well enough.
Otherwise, Walters plays 25-40+ minutes looking increasingly sluggish over 25. Smoothy plays 30+ minutes, the team gathers momentum. This is our killing time. Then Walters returns, Smoothy disappears into some mystery position - lock, I think - and the team becomes a rabble. We usually lose this period.
If we were to drop Walters - which will never happen until he retires - and bring in Mozer, he might be an improvement at hooker, or his inexperience might cost us. But he's a pure hooker who covers no other position, and we'd lose Billy's utility.
If we were to drop Smoothy and bring in Mozer, again we might gain something at hooker (or not), but it would otherwise be a like for like.
To solve our bench problem, therefore, we would need to omit two of these players, and bring in a more versatile, faster utility. Humour me here: but one example might be:
Mozer at 9, Madden at 14. Mozer would need to play long minutes and be better than either of our current hookers AND Madden would need to expand his positional play, particularly dummy half. He is fast enough and has the ball skills to play wider. BUT, he's unproven, and untrained in that role.
Otherwise, we look at replacing Hetherington with a Capewell clone. Which would allow us to bench two middles like Willison and Te Kura. I've liked what I've seen from Josh Patston for this role. But I wouldn't like to say he's a better hitman than Hetherington.
The issue with all this is the players we have are all good enough to make the team on their own merits. But someone we rate will have to make way for someone we rate lower, for the sake of insurance.