I thought the assumption from the start was Batman and/or Lex study krypton tech to invent Kryptonite and their power suits, either together or independently. Lex and Batman working together would almost make this mess make sense. Plus movie Lex finally gets to be an actual threat, because he had the goddamn Batman helping him prepare. Lex would have the means to beat Superman, but Batman can trump Lex, that sort of thing. (god that sounds bad, I know. But Lex has been Iron Man for what, 30 years now?)
I don't really recall but in Man of Steel up until Zod stripped down to his underwear weren't their suits the source of their strength as much being powered up from our sun? They were wearing masks and shit and actually limiting themselves, thus why they weren't flying etc. Zod goes from choking on our air and bleeding out his ears to matching Supes in less time than it took Kevin Costner to die for no reason. The implication was Zod with all his military experience would have wiped the floor with Clark if he had taken a weekend to hang out on a beach in Florida first.
(haven't seen MOS since theater)