Simple bobcat-front end loader would probably not be able to cope with martian soil.
Unlike earth where water and plants continuously make it finer grained and easy to move, mars has significant rock everywhere, and surrounding craters the the heat of the impact Glassifies the soil.. Which is incredibly hard as well.
Boulders have not been worn down by erosion, and even in the reduced gravity can weigh several earth tons.
Any road building project will likely need explosives or a VERY VERY heavy duty dozer with a high mass blade capable of shattering the rock, and pushing rock formations that weigh more than a semi-truck. *not sure we can build such a dozer with current technology... let alone transport it to mars*
The dozer would also have to be built to resist shocks from rock sheer that would tear a rover apart the first time it encountered one. IE: Isolated and shock dampened electronics, and a intenrnal combustion engine for power... batteries, electrical motors, RTG's, and pretty much any current technology would die rapidly as it was literally shaken to death and exposed to rapid high/low torque variations. It would have to be engineered unlike anything else on mars... Built better than a tank...
Lubrication and oils for the joints is also a severe concern as the thin atmosphere will deplete many oils and greases rapidly, the sand particles may be incredibly abrasive(They do not have water to wear them round), and the cold temperatures will cause the metal to be more susceptible to wear.
I imagine tubes of stabilized lithium grease will be a top martian import from earth =/
Anything a bobcat type extension on a rover could clear, any decent martian designed truck could simply drive over.
I agree however with GPS. It will be on mars.. it is too useful and simple to not have it. An entire GPS network would only take maybe 12 sats in geostationary, and they would be incredibly simple as you pointed out.
Farm implements are a possibility, but the atmosphere on mars will not sustain earth based plants, except perhaps at the bottom of a deep hole.. Now if you put those plants in a dome and put martian atmosphere at 20X pressure, Things like lichens and mosses probably will grow. *no one really knows for sure*