Do you think If I change the screen led by one compatible with Magic Pie 5 could work well like before?
The Pedelec function of the MP5 controller
(in conjunction with the correct MP5 compatible BAC-601 Smart Display) should work just the same as it did with your previous MP4 controller
(assuming all the programmable parameters are set exactly the same).
Without being able to select the different levels of assistance, which are only available with the Smart LCD display
(or Bluetooth dongle and suitable Android phone), the single fixed level of pedal assistance is not very nice to use, and there is no easy way to turn it on and off other than physically disconnecting the pedelec sensor.
In fact, before I had the Smart display for my MP4 I actually removed my pedelec sensor because I found the pedelec operation to be somewhat annoying.
Since fitting the Smart Display
(and refitting the pedelec sensor) the pedelec is far more useable, but to be honest, I seldom use the pedelec function, as I much prefer being in full control of the throttle.
But at least I now have the option to use the pedelec if/when I want to.
Hopefully, fitting the later MP5 Smart Display to your bike will return the pedelec operation to the way it used to work before your controller died.
Alan