Physical Therapy companies that help reduce fighter decline, limit/recover from injuries, and preserve hiddens and physicals (from declining). Doesn't prevent it, but should help reduce it for a high price. Maybe use of it could potentially reduce injuries received from fights.
Hyperbaric Oxygen Therapy
etc. etc. etc. Details would need to be discussed. Hashed out. etc. Just think it'd be a really good idea for a company if hashed out properly and could be a really good money sink for older fighters in their prime.