Awesome post
This was something I was thinking about the other day. The arrival time of the centaur is so early because Brits are assumed to have to spend fuel on emplacements or the AEC/Bren but as it stands those units are lackluster and emplacements are too easily killed to justify their fuel cost. I would add infantry upgrade tech to the list but USF and soviets don't take into account infantry tech when calculating teching costs so it seems likely that infantry tech is considered non-essential.
I see the solution to this issue being threefold.
1. The AEC/Bofors need to provide a stronger mid-game advantage. In short there needs to be incentive to get either a bofors or AEC instead of entirely skipping over both to fast tech a tank. These should be bonus tech used to gain a mid game advantage the same way a T70 or Luchs is.
2. The fuel cost of emplacements needs to be reduced and/or removed. The change to brace was necessary but has left emplacements hardly worth the large fuel investment. The mortar pit probably doesn't need a fuel cost since it is the only form of indirect fire a British player has access to that doesn't cost muni while the Bofors and 17 pounder just need to cost less fuel. Despite the cheaper price the large popcap of emplacements will ensure they are not spammed.
3. Increase the price of T3. British tank tech needs to be scaled so that if no fuel is spent it arrives around the same time as every other faction. This should be ~170FU for the first tank assuming no additional FU is spent. Building a mortar pit won't affect tank arrival time while going for the AEC or Bofors would be considered a timing attack meant to secure mid game advantage at the cost fuel and therefore would slow medium armor arrival time.
Put those three changes together and you probably fix the centaur arrival time as well as making emplacements and the AEC desirable again.