I'd give my votes separately to these ones:
ttrr - definitely requires the most time and skill to get better at it
bungee shopper - altho I'm not sure this is a league related scheme, but still one of the top hardest in my opinion, since everything that is bungee related in the game, is hard to work with
bungee race - ^ same goes
wxw shopper/and roper - I'd put these ones the next, any newbie player can practise them easily, but playing your turns in a really fast and effective way takes more skill and time
mole shopper - ^ same, although some molers can play this scheme almost in a pixel-perfect way of digging and opening tunnels, so I guess it takes tonnes of practise and time
> then comes all the rest. they are easier to learn (on my list, at least) I'd most definitely put all the roping (and bungeeing)-related schemes in the first place, then the rest in descending order.