From what I've seen Psychics completely dominate this tier. Between Mew, Alakazam, Exeggutor and Starmie make it really hard for Hitmonlee to function. Which kind of sucks since his powerful fighting moves would be much appreciated to hit things like Snorlax. Maybe a set taking advantage of Reckless would be good? Hitmonlee would be very difficult to switch into with with Reckless. OHKOing Alakazam, and even Starmie after SR and a layer of Spikes.
Also earlier today in #Pokemon we were trying to come up with Dragonite stops, since it is very difficult to actually beat. Cloyster, Slowbro and Rhydon appear to be the best ways to defeat Dragonite in RBY Cup, so unless you have a perfect plan to not let it set up you'll need one of those!