Well...repulsors quite visibly hold up things...and repulsor tanks can run characters over without hurting them (EP1:TPM)...so they clearly are "action at a distance". It's hard to see how they could do this and not have HUGE tidal forces induced somewhere between the repulsorlift and the planet...but...well...I like the repulsors-as-propulsion better because it gives me a nice handwavium box to stick all the otherwise crazy stuff the ships can do into.
They could always harness dark energy in some manner, which would allow for the magical "action at a distance." For those who don't know what dark energy is: it's the opposite of gravity (Gravity pulls, dark energy pushes).*Sigh* Repulsors are just about as mysterious as the Force. =/
Another explanation could be that since repulsors contain subnuclear (Do they mean subatomic?) knots in space-time, it could just be a magical device that uses a planetary mass's gravitic warping of space-time to somehow move itself. Which would be another magical "action at a distance" solution.