What practices would improve this scenario for the power transfer
200m of 1mm diameter cooper wire have a 4 ohm resistance, you have to take into account the voltage drop on the line. If you need 2A at 5V the current through the line will be above 1A and the voltage drop above 4V, that means you could get under 8V at the top. 

You can find insulated DC-DC converter modules at Farnell but most have a minimum input voltage of 9V which can be an issue if you use thin wires as you see above. If you're not tied to 12V then you can use a higher voltage which will really reduce the losses. 

I don't think twisted or shielded wires are needed. A lighting protection yes but it's out my area of expertise.

Somehow you have to join the source and phone ground using a high value resistor 100k to 1M to avoid accumulating static charges in the insulated phone area which can damage the converter.