There are plenty of theories beyond the standard model. These usually assume new particles that could be discovered if these theories are realized in Nature. This is however far from being the case in light of current data. The Standard Model however features many conceptual issues and practical limitations so that it is generally considered as a low-energy limit of a more fundamental theory to be discovered. This is why theories beyond the Standard Model are designed and studied at the moment: to be prepared for the exploration phase at the LHC.

Concerning the fine-tuning, this is one of the conceptual issues mentioned above. This has nothing to do with the forces, but with the Higgs boson and the quantum corrections to its mass (and the fact that we have two different scales in the game: the Planck scale where we know the Standard Model mist be replaced my something else and the electroweak scale which is the currently probed energy regime). Many of the theories beyond the Standard Model address this problem.

I hope I clarified :) Otherwise, do not hesitate to ask. This is my day job ^^