Is thete any chance he would act as a mercenary in the Latin American wars of independence as Lord Cochrane did?
Might be too high up and famous to be allowed to do it. Cochrane was low enough that his involvement didn't create too many diplomatic headaches but the Spanish might see a great like Nelson being involved as the British government openly supporting the rebels and a possible act of war. He probably wouldn't have the health to do something like that anyhow, he wasn't a healthy man at Trafalgar and another decade or so of naval life and battle won't improve it.