You will need to have a field theory to go beyond what MOND in original form does. It does only modify Newtonian gravity in the non-relativistic regime, and it

You will need to have a field theory to go beyond what MOND in original form does. It does only modify Newtonian gravity in the non-relativistic regime, and it applies well at the scale of galaxies but does not address relativistic effects like the one we actually see. One example would be gravitational lensing . To be a successful theory of gravity you would need to be consistent with General relativity. That's the reason why you would go to extend MOND to field theory. The most famous framework would be TeVeS and it does have many fitting parameters.