I agree with what Bolt said above.
They need to give us more variations of obstacles to allow more valuable use for HMs.
Cut - aside from tiny plants, as Bolt said, we can have ropes, thorny vines, webs. Also, they need to bring back its ability to cut tall grass.
Fly - I really don't think that they will give us full ability to explore the skies. So, aside from ability to fly us to cities, they can use Fly in puzzles, such as going up a level or two inside buildings/caves with open ceilings/holes without available ladders/stairs.
Surf - It doesn't really need to be changed.
Strength - Boulders are so Gen 1. Give us something else such as cracked walls, heavy crates, or wooden planks that block doors.
Dive - RSE Dive mechanic. That's all.
Dig - Same as Bolt's ideas. Also, it can be used for digging up stuck items on the ground.
As for the others, I prefer them as TMs.