Is there a special jutsu to use the sharingan? Do you know the special jutsus to activate the sharingan? Obito is dead and Kakashi didn't have Itachi or Sasuke around to train him on using it. How did Kakashi know how to use the sharingan and how it worked? It would be considered even more rare than anything Deidara uses, and Kakashi seems to be using it just fine. Sand isn't light either, particularly sand in a gourd. So you are also indirectly implying that everyone that uses Suna ninjutsu would need to have their stats changed because they are carrying and walking around with a large amount of sand, which would slow down their reaction time to attacks?
Suna just like all the other styles in this game are limitless. A suna user being attack by a water user, would mean that the suna user's sand is now limited, should we limit it then or leave it the way it is now. The game has been predicated on not limiting things, why would we all the sudden decide to limit the amount of clay one has with them. 
The Sharingan:
Kakashi has worked with Obito so he has seen first hand how obito activated it. and we also know that there is no real hand signs devoted to its activation and simply that you allow the sharingan to use your chakra. (Which is obvious through the fact that Kakashi's Chakra is completely exhausted after its use even though he has a larger amount than sasuke who can continuously use it)
if you mention the Byakugan then youll notice that the byakugan DOES need the special hand signs which only a hyuuga knows and seeing as how the hyuuga clan wont pass it to any outsider gaining it through an operation would be pointless.
thats basically what happens for Deidra's jutsu, you know that no one else will teach you how to activate it because there is only one user at the moment. and even if it was a clan ability wouldnt it be kept secret seeing as how its powerful when used properly?
We also said that it IS possible to restock your sand through events where you stumble across a rocky area or make it so you can get some from the mines but a higher risk of death.
you can also have it sold from the merchant.
Suna can be used with rock from the groound. its true that sand may be heavy but your creating it from sand in the surrounding area as far as this goes and even if you did carry some you simply need a bag full and not even a large one at that. sand may be heavy but not heavy enough to weigh you down too much. it is also possible to re-use sand as gaara does. it goes back to him after wards does it not?
as for suiton, as stated earlier you create your own water when you perform the jutsu. it has been seen done.
Katon: you dont need fire nearby to use it
Doton: there is earth everywhere
all the others dont need heavy materials.
clay isnt something that can be created through a jutsu as far as we know. all the others can be and HAVE BEEN SEEN happening.
