Mike and Ian fight is very much possible. Jeremy is on another weight division unless EK makes him cut weight like Ian's first opponent. Mike won by submission in the first round but he claimed that his opponent was much more of a beginner than him. Mike's a grappler too. Ian needs both disciplines at competent level to win the finals. Wen and Yuri pointed out to Jeremy that he needs to learn jiu-jitsu to counter it properly and he straight up declined. I hope this plays as a good reminder to Ian that you need to be well rounded to win just as Yuri said. Jeremy's distaste for jiu-jitsu could be his downfall later in the tournament.
Jeremy's first fight was a doddle. He basically just used his superior reach to pick off the guy, who couldn't get near him to score any points. Whereas, Ian's first contest was a total war, against a guy who a big weight advantage over him. In the second round, he came out determined to do some damage to Ian, who had to absorb quite a lot of punishment, until the opportunity opened up for a takedown. Once he had him on the ground, and used his body weight to pin him down, that early onslaught when he failed to knock Ian out, meant he didn't have the energy left to get Ian off him, and when he weakened even more, Ian got him into an armlock, and the fight was effectively over, because there was no way he was escaping that for a second time. I wonder, if he'll actually prove to be the hardest opponent in Ian's side of the draw, until he reaches the final group?
I can't see Jeremy dropping down a weight division deliberately. I think he'll view that as being unsportsmanlike. He'll want to win on his own merits, and not by taking advantage of a loophole. Also, I don't think he'd want to fight Ian, and if they're in different weight divisions, there's a possibility of them both ending up as winners.
And as far as Mike is concerned, if Ian believes Jeremy, he already suspects that Mike is one of the likely guys, that Lena might be fooling around with. So any fight between them, is going to have some added angst. And we know from his confrontation with Axel, that Mike has a bit of a temper, that he struggles to control. So if Ian could get him a bit worked up before the fight, and uses 'provoke' to stoke the fire even more, he might be able to get Mike to lose his cool, and attack rashly. If he's a grappler, he really wants to him to strike, because that will leave him open to a takedown eventually. Wear him out trying to knock him out, and then pounce when he tires, and get him into an armlock, which he's then too weak to resist. Ian just needs to keep his cool, and make sure Mike loses his. Which he might do, if Ian were to rile him up about Lena beforehand.
I started off with Ian learning Ju-Jitsu, because I think it suits his more compact body type. Whereas Jeremy's long arms and longer legs, naturally favour kickboxing. But then later I switched to improving his striking technique, after Yuri suggested it. Hopefully, we'll be able to keep switching between different styles of fighting over the coming months, between separate bouts. So Ian can become much more well-rounded as a fighter.
