2 years prep ... with his tech and the mind gem and the rsources and with the prep makes Cap unbeatable. With prep and the stuff he has access to um it lame but Cap might win. Think how BAtman wuld 2 freaking years of prep he can prolly take over the DCU in less but hey cap + the gem + crazy resources + 2 years .... I still don't think he will be able to do it by force prolly use alot of trickery and having people fight against each other and he would be pulling the strings. This would be the same if batman with a all that jazz came to MArvel he would have the same chances he might not need as much time b/c i think batmn's prep ability is already nasty.
With a ring of his own he will think to do something with it wither making it more powerful through his own resources or look into OA but like another person said it is heavily guarded but things can be done to get around it.