If you go to rear dics you'd need a new proportioning valve which sends more or less pressure to the front or back. I believe disk brakes require much higher pressures to get the same braking force as drum brakes at lower pressures.
For as often as one needs to change brake does out (probably 1-2x in the life of the car), its not even close to worth swapping out. If you want improved braking performance, the 2017 model upgraded to larger brakes up front where it counts.
View my fuel log 2015 Mirage ES 1.2 automatic: 49.0 mpg (US) ... 20.8 km/L ... 4.8 L/100 km ... 58.8 mpg (Imp)