This is seriously needed. You should be able to assign server variables, block variables, player variables and client variables. This would open up an immense amount of opportunities. You would be able to make your own variables with their own names.
Server variables are global variables server-wide.
Block variables only apply to the command block using it.
Player variables are assigned to the player. When the player dies, the variable goes away.
Client variables are assigned to the client. When the player dies, the variable stays.