O'Donnell is definitely one to persist with and should start next year. We saw very clearly this year though that he's a work in progress. He makes a lot of errors, particularly in defence. The upside is clear though and the issues he has are entirely solvable through coaching and experience.
Walton is a glue guy. He's been around the team for a long time and has also dealt with a lot of adversity. In my view you indisputably need a couple of guys like that in the squad (Hugh Sinclair absolutely falls in this category too).
He's not a plus starter and if that is your plan for your best team it won't be a position of strength. It also won't be a position of weakness. If you want to compare him to O'Donnell though, I'd say you would expect to see better games out of Walton more often than O'Donnell.
Ideally you'd enter 2026 with another centre option that you think is going to start next to O'Donnell. Both of those players would need to be firing though because Walton will be pushing his case for either position.
In terms of recruitment, I think you have to elevate a number of talented young players from the under 20s to the main squad and hope they remain on the periphery. Eamon Doyle is obvious in the forwards and I don't know if Liam Grover is a chance but I'd certainly be trying to sign him. He's a fairly strong chance of going to league though isn't he?
The team is in a position where it's not a couple of players away from being a contender. Time to take a few more risks and back more young players as being more important to the squad.
For example, someone like Ben Grant was really good for the team this year but there needs to be a plan that there's a younger guy with a higher ceiling trying to push him out of the XV/23.