FWIW, Lopez isn't a FA and seems to have a fit in Atlanta as just that role that you're describing, so he specifically probably isn't on the market.
As for the offseason on the whole, with napkin math I think that roster is probably ~55 million over the LT, which even if there's a more aggressive 'with Ohtani' budget due to his revenue bump, doesn't strike me as particularly realistic. Especially with no huge deals coming off the payroll after 2024, ~25 million thanks to dead money(Mancini + Bote), Smyly, and the catchers.
My working assumption is that they'll be willing to go into the LT this year(even without Ohtani), but probably something like ~10 million without him and potentially ~20 million with him. As such, most of the big spending would probably coalesce around something like Ohtani + Candelario or Bellinger + FA SP + bat(e.g. Alonso).