I don't understand the M20 timing buff for the following reasons:
A. Having snares on all rifles after teching is a massive buff for the M20 already.
B. Shortens an already short early game phase.
C. Most people are stuck in this weird mindset that LVs HAVE to function as a shock unit. This becomes particularly apparent in the 222 vs AEC and M20 vs 222 matchups. In both those cases the superior unit arrives around the same time, however this doesn't mean the weaker unit isn't viable anymore. You just have to protect it with snares or AT. In the Live version this is done by the LT bazooka which needs to be equipped immediately with the M20. In the patch you have snares on all your rifles in addition to this.
D. The M20 provides massive utility (Sight, Mines, AA, Smoke, Harrasment) even in the later stages of the game. It doesn't have to be a pure shock unit.
a) cons can also have early AT nades, but it never made M3 more viable or last longer
b) arrival of lights do not end early game, arrival of light tanks does
c) well, you've answered yourself here, if your light is outright destroyed or constantly zoned out, its value diminishes greatly, so it needs to pay for itself within the short window between its arrival and its hardcounter arrival, just bacause M20 or Kubel survived 20 minutes doesn't mean they actually achieved anything in last 15.
d) in a perfect world, all lights are useful to some degree at all stages of the game, if only to provide sight and some support ability, in practice they are way too fragile to do anything outside of their initial shock value time window, because if it can't handle dual ATG alpha strike, its not going to provide you any value in mid to late game