Why refuel satellites? Why not let the "Restore-L" instead tug the satellite with its own engine? It should be much easier and safer and one doesn't need to care about what fuel type the satellite originally had.
Because a "tug" isn't needed. No "engine" is need. The propellant is for attitude control. Attaching another spacecraft is not that simple. The mass properties of the stack is different. The attached spacecraft would interfere with look angles of sensors and instruments. It would require sending commands to two spacecraft to point and take data.
Hubble is pointed with reaction wheels and was boosted to higher altitude by the space shuttle. Wouldn't that be applicable to many satellites in LEO, but with a small tug in place of the shuttle? During satellite operations the tug could be undocked and at standby nearby until next orbital correction is needed, or go off to another servicing mission.
What about designing satellites such that its fuel tank with thrusters is replaceable? When it is getting empty, it is undocked and discarded while a tug brings a new identical fuel tank with thrusters to replace it. No need then to transfer fuel in microgravity.