Yes I'd love to see the older ships as I own a old Connie myself (named Golden hind after Drakes ship) But the problem is if you upgrade the weapons and BO where do you make space? a Constitition in Kirks time was 400 crew now its 200...makes sence in the same way the Iowa class class has a reduced compliment to reflect a kind of crews' comfort zone' lol You didn't even have you're own bunk in those days and had to rotate it between shifts. But back to you're point , if you want to make a old ship modern you have to make space for the power demands. In ships like Excelsior its no problem cause they had 10 dual mounts in sauer alone so it's easy to under stand how 10 old dual mounts can translate to 2 phaser strips .The power is there. but how could a old Consitition have modern weapons? It would have to give up space for the new power lines. In other words you'd have to give up something to gain something ...50 crew? no shuttle bay make it all engineering? nah it ruins it.
as for weapon mounts...if you want a quick and dirty upgrade <easy>
then your stuck with the number you have.
all you can really do without pulling into space dock and whipping out the cutting torches is the following
Upgrade the current BO stations.....maybe add one
er...thats about it
weapons themselves can be upgraded normally...you only get a couple of mounts, put some good weapons
shields are already upgradable
as is deflector, impulse engine ect..
if you wanted to add something...different to these 'upgunned' older hulls...you could
make them harder to ID....the enemy might know you have tougher weapons onboard but they
don't really know how advanced your BO stations are.
a STO constitution class upgraded to rear admiral might not be able to go toe to toe
with a tier 5 ship, but should be able to put up a fight with a tier 4...and clean a tier 3s clock.