The goal of this change is to increase the types of viable empires that can exist in the game. Currently, as in most 4X games, racing to gain the highest technology is the optimum way to play. A large empire with the Law & Order doctrine can usually dominate all others.
This change adds disadvantages to high-technology that can only be compensated by having the Science & Technology doctrine. Thus empires must choose between becoming large (via Law & Order) or technologically advanced (via Science & Technology).
Technological Disasters
Large empires risk rebellion secession; the Law & Order doctrine reduces that risk (by a factor of 10) allows such empires to grow. Analogously, the risk of technological disasters increase the more high-tech worlds and empire has. The Science & Technology doctrine reduces that risk, allowing empires to safely lift all their worlds to high technology.
S&T Capitals and Sector Capital
Capitals and sector capitals act as foundations. [Though perhaps they have some extra structures.]
Balance
We need to balance the game such that a Science & Technology empire with the maximum number of worlds can produce a military as strong as a Law & Order empire. We may need to adjust combat values of high-tech units.
Excellent, this adds a clear wide/tall dichotomy. Please note that right now there does not seem to be a practical limit on L&O empire size because of the overwhelming effect imperial guards have on secession risk.
Planets with high fated TLs should not contribute to disaster calculations as much as uplifted worlds do. These planets should have intrinsic value to empires (similar to how planets with "abundant" deposits are never a liability.)
Interesting addition, I like it, and was hoping for some new things to be done with doctrines this round. What is the consequence/punishment in terms of "technological disasters" for uplifting all worlds to a high TL? For a "singularity" type event - where many worlds flip to independent, a mass lowering of TLs and increase in revolution index, or sector capital secession similar to L&O? Does S&T merely reduce risk or also provide some other tangible benefit (like how L&O provides a force of fanatically-loyal Imperial Guard which never defect - very useful!)
As an experienced player I would still opt to use L&O because of the Imperial Guard, and there is no hard limit to how many worlds one can conquer, even if their TLs are limited as such. A 1000 world TL7 empire (with no SC limit) will win out over a 200 world TL10 empire (with a 2 SC limit) every time, by its economic might alone, it's been proven before. So I believe S&T should provide some really compelling advantage/unique unit in that regard.
IF Mesophon trading is fixed and players can buy more than 1000 ships at a time, this means there are 3 viable playstyles: the trade league (T&E), the technocracy (S&T) and the good old hegemonic imperialist (L&O). F&M and S&H would probably then be underpowered in that regard, that can be addressed later I think.
I think that it's fine for there to be transitional or niche doctrines - doctrines that make sense when your empire is growing or is on the ropes and trying to survive a war but which are not a balanced option for mature empires.
Mechanically it wouldn't be too much trouble to give the ship doctrines' sector capitals a productionAdj for some of their ship types. They would still require the same amount of resources but their labor cost would be lower, so capitals could crank out ships much faster and allow planets that would otherwise be yards do other stuff like build components or infantry. In this respect smaller empires could punch a little above their weight and empires that are struggling in a war might see an advantage to switching to one of the ship doctrines.
I think that the value of sector capital jumpbeacons may become more apparent now that beacons aren't instantaneously built (assuming that this feature is retained, it still needs to be playtested). F&M empires will be less vulnerable to leapfrogging and beacon denial since player will fortify their capitals anyway. Switching to F&M (or T&E, I also put beacons on T&E sector capitals) will give players a free instant jumpbeacon on their imperial capital and getting an instant beacon could end up being a life-or-death matter in some cases.
If Mesophon trading gets fixed I expect that in a long game T&E empires will be grossly overpowered without additional balances, since aes are not subject to attrition, are "invisible" to other players, and do not affect imperial might; meanwhile, T&E empires can sit comfortably below other empires' imperial might for a long time before striking. The only thing that has prevented this from being more common the awkwardness of the Mesophon interface.
The more that I think about it, the more I think that adding full-radius jumpbeacons to T&E capitals might be too strong - but we can see how it plays out in actual games. Certainly T&E will also be disadvantaged by technological disasters and TL limits.