For MNK I'd like to see a new combo with fresh animations, our animations look very outdated except for Demolish and Dragon Kick.
I'd also like to see some kind of a Enochian system or Midare involving a big hitter with lots of kicks ala Hyakuretsukyaku https://www.youtube.com/watch?v=dFyyeiPXW8Y .
I think it'd work with a cast bar sorta like Midare but the kicks happen within the cast time and finishes with a big hit.
It'd break up the monotony of the pace too.

Overall I think the base of MNK is really good, it just needs something more.
It kinda feels to me like it has a good base but the fluff is missing and it's too repetitive.

In Blade and Soul Kung Fu Masters had a grappling mechanic which would be really cool too ( 4:00 ) https://www.youtube.com/watch?v=cHpB1x56d5U .
That's obviously not going to happen xD, but I think it'd be really cool for smaller enemies and against bigger enemies it could just be a big hitter instead if you used it against them or other enemies that couldn't be grappled.
That's just me dreaming tho.