For the amplifier and signal conditioning: the amplifier is always limited in its common-mode voltage range when there is no isolation. Usually 80 to 100 V is the maximum voltage that can be withstood. Then there are many ways to amplify the signal across the shunt resistor, from the most discrete to the most integrated. To have good accuracy and performance, the amplification phase needs to have very well matched resistors around the op amp. So, the easiest in order to have a guaranteed performance would be to get an integrated shunt with op amp. It is the smallest and most precise shunt solution, but limits the possibilities to certain current and voltage levels. Furthermore, it usually features a relatively high impedance value that is superior to 2 mΩ, and hence consumes quite a bit of power.