I’d play 3-4-2-1.
I think now Brooks has gone, you have no bona fide winger. I think a front three of Bamford supported by O’Hare and Hamer as two 10s allows good creativity and goalscoring.
You can then free Seriki and Burrows/McCallum who most would accept fit the wing back role well.
Already it feels you are making the best of what you have without unwanted or expensive recruitment.
Presently you have Peck, Arblaster and Rothwell for one role and then need to recruit a more robust defensive partner, be that Riedewald or Phillips, Choudhury, or similar, a couple anyhow. I wouldn’t be shocked if Wilder tried to get Lundstram back. Not saying I agree but it’s the sort of thing he’d consider.
Then a three allows to cover for some shortcomings. I’d probably have Tanganga-McGuinness-McCallum if the game was tomorrow but you’d focus recruitment there to improve that lot. If you end up ideally with maybe Walker-Souttar-Tanganga though appreciate a LCB is preferred.