So, as shown with probending, the probenders do not use the BASIC combat moves, they use much simpler, and smaller moves for each element. Here are what I have come up with:
DiscThrow:
For those of you that have seen earthshard, it'd be rather similar to that. But instead of using a full block, it'd form a stone/sandstone slab that you could shoot out at the opponent. This would provide more knockback, and also provide as a shield if it is left floating in the air in front of you. The earthbender would not be able to reaim this disc after it is thrown, it would just go on to a configured range. Another earthbender could counter this by shifting at it, and it would dissipate after 1 second, along with having a slight cooldown so you may not spam the blocking mechanism.
WaterSlap:
We all know that there is a hosing foul in probending, so torrent or watermanipulation would violate this with being far too large. I'm not exactly sure that this can be made, but think of a smaller watermanipulation that wouldn't be created by a source block. Perhaps a 1/2 block 'disc' of water that would launch at the opponent, yet again this would provide more knockback than watermanipulation. The waterbender would not be able to reaim this shot after it is thrown, but a waterbender may counter it by shifting at it to make it dissipate after 1 second, along with a slight cooldown so you may not spam the blocking mechanism.
EDIT: You could also redirect this only ONE time after it is shot at you, thus allowing for a small volley. For example, if I shot it at someone they could shoot it back at me, but I couldn't send it back again.
FirePunch:
As you see in probending on the show, firebenders don't really send 'blasts' at their opponents, they send small shots created by a punching motion which is faster and deals more knockback than a damage variable. Perhaps this could be a much smaller -- but slightly faster -- stream of fire particles that shoot towards your opponent. This would deal more knockback than a fireblast, but no real damage. The firebender would not be able to reaim this shot, similar to how fireblast currently is. A firebender could block another FirePunch by shifting at it when it is within a range and would vanish after around a second. This would have a cooldown so you may not spam the blocking mechanism.
This is my first suggestion in a LONG time! I hope you guys like my ideas, and please comment what you think!