[BlackFly]

Well, Newtonian physics can be readily derived from General Relativity as a sensible approximation. General relativity has a sensible backing in Hamiltonian mechanics.

The relativistic version of MOND, TEVES, is known to be unstable and its action is a complete mess. Moreover, since the action is attempting to add a scalar field and a vector field (which in relativistic theory is just a matter field) it is exactly proposing the existence of an unexplained matter field: dark matter.

So in the end most people disregard MOND.