Build on McPvP used to have a very useful command - /flyspeed. Re-implementing this would be great.
I've forwarded this on, thanks for the great idea!
I think having /speed is easier and it will change your speed if you're flying or walk speed if you are on the ground.
If you want walk speed there should be /walkspeed. I don't think many people want their flyspeed to also be their walk speed though.
/speed when you are flying changes your fly speed, if you did /speed when you are in the ground you an choose a different number.
2 separate commands means less confusion. Mind = Blown.