I was thinking about this aspect of this theory as well, and certainly, the Malaysia Air pilot would not have been able to mind read the lead pilot, but as far as the distance and position, there would be a very rudimentary solution to this. In WWII, the Lancaster pilots who flew the dam buster missions had to be as close as possible to an altitude of 60' above the water for their drum bombs to skip to target. Altimeters at the time were not that precise so theater spotlights were fixed to the bottom of the fuselage, one up front and one towards the rear, and were angled to converge at 60'. The aircrews knew if they saw two beams they were either too low or too high, but when the spots merged they were just right. One could similarly use green lasers angled to converge at virtually any desired distance one needed them too, and make a simple bracket with two laser pointers that could be mounted inside the trail plane's windshields and visually maintain a precise interval behind and above another airliner...
Most airline types are lit up at night like a Las Vegas strip joint.
Passenger windows, strobes, the legally required running lights, lights focused on the vertical stabilizer...etc.
No haze at that altitude, at close range even starlight alone would enable the following aircraft to see the other.
As for the difficulty in joining up, look at the map and at how close Singapore is.
From his altitude, he would have no trouble at all monitoring Singapore’s departure frequency, the clerance, etc.
An the clibing aircraft would be covering the ground at a much lower rate than one already established at altitude, so he would be able to catch up.
Sure it is tricky, but who knows how long he had planned and whether it was genius, luck or never happened?