a) cons can also have early AT nades, but it never made M3 more viable or last longer
a) m3 and m20 can't be compared due to performance and different usages. M20 is closer to a light tank in terms of function than to the m3, wc51 or bren. Also cons don't automatically get at nades once m3 is teched so the comparison doesn't really work in the first place. Pls trust me on this one, I've used that unit a shitton. It also shouldn't die if you use it well.
Random dane cast of me using M20 in an older patch: https://www.youtube.com/watch?v=j_RIcJecZ5I
Also watch ML1 Tiramisu vs Quiritz G1 on Mill Road for Ostheer vs US matchup in current patch.
b) arrival of lights do not end early game, arrival of light tanks does
By early game I mean the infantry+ultra light phase. Question of semantics.
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.
You're mixing up Ultra Lights (Kübel, Bren, WC51) with Lights. The "being constantly zoned" out thing you mentioned is exactly what I was talking about. The AEC got absolutely slaughtered in the patch because people considered its timing unfair relative to 222. This is because people want to use the 222 vs brits exactly like they do vs USF and Soviets, meaning as a unit that immediately dominates the field for a certain time window. Obviously that's not doable vs the old AEC timing but rightfully so because Brits lack snares on their mainline and rely on the bren carrier (which requires protection vs 222) vs sniper starts.
The same problem exists to a lesser degree in the context of M20 vs 222. If you upgrade your LT bazooka straight away and keep it close to the M20 the 222 will be kept busy chasing away but not killing the M20 and you transition comfortably into Stuart. Now add snares to that to limit the 222s ability to threaten the M20 even more and Wehrmacht ends up in a very awkward spot vs 2 light vehicles. 2 Light vehicles if played well are very underrated. 1 Pak is potentially not enough to deal with them, 2 Paks is too big of a manpower investment.
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
This perfect world exists already for the most part.
And once again youre mixing up ultra lights with lights. First of all about ultra lights: Kübel is a super useful maphack. WC51 can use mark target, artillery and can be used as a cheese bazooka/satchel bus. You're right about the Bren. (although it does haved incredible early-early mid value so the drop off is sort of justified) M3 is just shit in general but theoretically it can be used as a capping unit.