... except that the D7 was always presented as a peer combatant and deadly threat to the Enterprise. I don't want a peer combatant. I want to overmatch the D7, So that when it comes to smash our stuff, it will be outgunned, outmaneuvered, and incapable of inflicting critical damage or even running away. I don't want to fight fair, I want to flat out murder every Klingon Battlecruiser that dares set a toe over the border, with the only way they can win being getting lucky.
Honestly we have very little to go on in terms of how the
Constitution stacks up to the D7 in TOS. We know the Connie was built to to fight the D7 and can infer Starfleet apparently thought it was up to snuff. We see the Connie fight a D7 twice (debatably in
Errand of Mercy, but it's shown as a D7 in the remaster), winning both times, despite the Klingons getting the first shot in both engagements. If I had to judge I'd say it seems like the
Enterprise is somewhat superior overall, although not massively so.
This video has a summary if you're interested.
More broadly... this does not change the overall point about needing to be able able to make cost/benefit judgements, but it feels like this discussion is getting very repetitive so I'm going to leave it here.
Same deal, we need strong spaceframes today. I'm willing to invest in so far as advancing our Shield Tech, because that's useful, but Large Type-1 doesn't really pay out until 20-30 years down the line, and by that point, the purpose we built these for will be finished.
But even until that time, it provides us basically the same shield strength as a Standard Covariant, and at lower cost. If you're planning to go with Light Covariant then I understand your reticence here, but otherwise it seems like a good deal? Saves money and gives the design room to grow.
Also I wouldn't underrate the importance of the
Constitution in the TMP era - even after this war, we are still going to be staring down the Klingons over the neutral zone, and having one of our major combatants continue to grow stronger over time is a good idea IMO. Thinking of this ship as a short-term investment is probably not the best idea; we're looking at a longish service life and a long cold war with the Klingons after the Four Year war finishes.