Given that McGregor walks around at 180 to 190 pounds, I'm not surprised McGregor would propose a MW fight so he has no real weight cut to contend with and can eat his normal food preferences.
Whether he is serious about Chandler being the opponent, I'm not so sure. Is the silly laugh at the end of the video over the MW designation or the fact he is trolling Chandler and will ultimately pick someone else for his next fight?
I actually think Chandler is a good opponent for McGregor as Chandler will want to stand in front of McGregor and bang so its an interesting fight. Despite being a solid former D-1 wrestler, Chandler really doesn't use his wrestling much, which is a mistake IMO. Given McGregor's history of gassing early, I would definitely mix wrestling / clinch / standup to tire McGregor. Despite McGregor's decline, he is still a very accurate striker who can cover distance quickly with power. I would also use the calf kicks to wear down McGregor as he didn't seem very good at defending low kicks vs. Poirier. I think this fight would be over early. Somebody will get a KO/TKO or submission. I can see Chandler damaging McGregor and getting the RNC finish or GnP finish. I can see McGregor catching Chandler with an overhand left which hurts Chandler and leads to a finish. McGregor might regret fighting at 186 as he isn't used to carrying that much weight in a real fight with all that adrenaline. His gas tank problems might be worse than normal.