we made a full circle geoff. okay, let first discuss what our battle landscape is like. becuase your way seems to have a landscape different from others, at least according to certain posts. do we want a roughly equal mixture of different sized ships? if the answer is yes, parallelism is need. if not, a traditional progression will suffice.
think of hull sizes as something you'd just research once, like chases in SMAC. What determines how good your ships of a particular size are is the other components that you'd stick into the ship design. Many of those components would be usable (or would have versions usable) in several different ship sizes
i agree with you. the differrent sizes or chasis are researched once. you stick whatever components in there. the different chasis may comprised of better "power plant" or something else that makes their performance in certain area better than predecesor. or the improvements could be a bigger hull size than before.
note that in your design, you also have competing factors: improvement in certain measures of the ship by increasing size, or just improving the measure and sticking it into your ship.
....... medium .................
............... large ..........
....................... huge ...
where each size listed is just a single tech. Improvements in ships with time would be due to researching better parts, not researching the hull size again (since you already know how to make ships of that size).
this is a traditional progression. i don't have much problem, except i think you don't understand how such a tree will play out. i'm saying it will inevitably lead to large ships vs. large ships, like all other games. let me explain why this must be the case below.
T can be normalized by cost if you like, that's not the important part.
i think this is where you have the wrong concept. T cannot be normalized. each generation of ships must have greater T.
research is considered growth part of rps macro-strategy. that means research must pay off more than it's investments in the long run, or else research serves minimal purpose for the player. therefore, T must increase, and connot be normalized to the same T after normalization.
the only way i find your idea might work, is that the landscape changes over time to facilitate a strong need to research a new size to fit that niche. that is very difficult to have it worked and balanced out for the player to justify a large rp investment to do a measure better and worst of other measures. we would need to think very carefully about our evolution of battles and avoid having "weak" or useless niches. Without increase in T, i'm not sure if the idea will work. i'm afraid at competitive games, players may only use bread-and-butter ships and skip investments in large hull sizes.
evolution of battles is certainly very interesting. however, it requires a workable lists of niches/measures that we can play with to start brainstorming. the problem i have is envisioning several niches that will developed that would justify large investments into a new size with constant T.
just a thought, you progress from scouting age -> defense age -> strategic targets age -> domination -> transcendence age... so you research tiny ships for faster and better scouting, then you do medium ships for defense, then large ships to attack and protect strategic spots, then you build huge support ships for your armada to eliminate players, then you build super large ships with weapons that blow things up from a different star system. all this could parallel with economic developments so you get techs and infrasctucture to utilize and find special resources in end of defense age. I suppose you would want a mixture of ships at each stage of evolution. though, one possible big flaw is that strategy are more or less set from beginning of the game. that might add some monotonous that players might find boring.
another thought: instead of ship sizes, maybe its better to say ship classes. for example, there might be a class of called multi-dimensional ship. it has good stealth and uses powerful multi-dimensional weapon. the ship isn't any bigger, but just stealthier and can mount better weapons. maybe you can throw in some disadvantage like moves slower. concepts is the same, just better sci-fi, makes ship size ratio irrelvalent.