Yeah, I have my engineering degree and knowledge, and work on product design and manufacturing, have a lot of knowledge about corrosion and other stuff metallurgy, material fatigue, stress cracking, cyclic use, stress cycles, etc, and some scientific ideas about how you’d design warships in space, but communicating all of this is like… difficult for me.
With the generous refit rules, if they gave a way to replace Phaser Emitters with Phaser Arrays, there would be little reason to have new hulls at all.
I think I can actually see what you’re getting at (you’ve done a good enough job that I, an interested non-engineer, had a good idea of what you’re talking about), and I get the distinction about refitted hulls vs updated designs. Certainly I can see that it would be possible to reuse an existing design with newer technology - which would explain a lot of the Excelsior and Miranda reuse.
But at the same time, I think technology progression has an effect here - especially over a century. The Constitution would never have been able to support the larger nacelles apparently required by the transwarp system used by the Excelsior for example. The old TNG Tech Manual went on at length about how the understanding of subspace structures and warp bubbles influenced design. I think it would be reasonable to assume that 24th century warp drive would not work that well with a 23rd century spaceframe.
I think you can see this sort of thing with real world ship (and certainly aircraft) design: newer technologies have an effect on the appearance of the vessel - even if the basic concept remains the same. Compare an early 19th-century warship to a modern one, and there’s quite a contrast.
Although I will admit, the contrast is much more extreme in Star Trek! 
I think “bigger is better” is the design philosophy of the show’s designers rather the Federation.
Everybody wants their ship to be badder than the previous one, interiors to match, like the pinball arcade they made for the Kelven Enterprise bridge, or its three football stadium engineering, and the HUGE bridge on the Discovery.