When you go to the training grounds you can only spent one point at a time, this prevents you from being able to have two level 12 or 13 elemental jutsus....I also later implaied that you could to combinations with the elements...using Fuuton or Raiton to incresse Suitons power....
While, I can see where you are coming from, you can still have "those" events in the forest that will allow you to increase your specialty at a "certain place".
As for the combination of jutsu in the sense where this jutsu increases this jutsu, possibly (with implementation with the system already in place).
As for the combination of jutsu to create a new jutsu, no.
If we add the ability to have a fully fledged skill of having multiple chakra affinities, which are basically specialties, it would be far to easy to rank up.
PLUS, it is called a specialty in the game. . . You cannot have TWO specialties, then it would not be a specialty.