Star Fleet NEEDS ships mainly designed for combat and not just a handful, but a fleet of them in case of war with whomever.
I couldn't disagree more. In fact I'm pretty sure their lack of pure combat-oriented starships is the main reason why Starfleet is so effective as a peacekeeping force. As I've pointed out many times on this board, 90% of the shit that threatens the Federation is non-military in nature; from flying neural parasites to planet-eating monsters, from incorporeal serial killers to full fledged pissed-off deities, from omnicidal space probes the size of coffee machines to omnicidal space probes the size of death stars, and so on and so forth. It's significant that Earth itself was threatened with annihilation on two seperate occasions during the TMP movies and neither of those threats had applicable military solutions; a pure combatant like Vengeance would have been the least useful ship in the entire fleet against V'ger or the Whale Probe.
The strength of Starfleet is its capacity to engineer creative solutions to unconventional problems, which becomes even more useful when conventional enemies start getting savvy. It actually isn't all that difficult to out-fight or out-maneuver the Klingons in a straight up engagement, but if the Klingons come up with a new weapon or come at you with some kind of crazy energy-dampening death trap based on lost technology no one's ever seen before, Starfleet science officers can devise a countermeasure in minutes while their Romulan, Klingon, Ferengi or Cardassian counterparts would have to spend six weeks reverse engineering it and going through the normal R&D process.
To quote Norman Schwarzkopf:
"The military is a hammer. Not every problem is a nail." Starfleet apparently took this to heart, which is why the entire organization is actually a giant Swiss Army Knife. USS Vengeance was one Starfleet admiral's attempt to convert the swiss army knife into a really fancy broadsword; that's all well and good, but what do you do if all the phillip's head screws on the planet Thessia suddenly go on revolt for better wages? (weirder shit has happened in the Star Trek universe).
Understand what Star Fleet is, but to have a fleet of just exploration ships with limited defense abilities invites attack.
DURAS: This is not your world, human. You do not command here.
PICARD: I'm not here to command.
DURAS: Then you must be ready to fight. Something that Starfleet doesn't teach you.
PICARD:
You may test that assumption at your convenience.
Having a fleet purely for exploration is all well and good on paper but in reality you must be able to project force
Starfleet doesn't "project force" nor do they have a need to do so. Their military applications are limited (by law, probably) to defensive operations of Federation borders and to themselves in interstellar space.
Beyond that, a typical exploration ship can take on anyone else's battleships on better than equal terms. Partly this is because Starfleet can draw on the top engineers and scientists from 200 planets and always has access to the best technology anyone has ever seen, but mostly it's because their equipment is sophisticated enough to quickly analyze and locate the one crippling weakness in everyone else's combat systems and exploit the hell out of it. That, plus the fact that their officers are a combination of warrior scientists and phaser-toting daredevils, makes them highly formidable for reasons that have nothing to do with firepower.
It's like if Indiana Jones and Neil DeGrass Tyson teamed up with the Mythbusters to take down ISIS. They wouldn't bother with air strikes, bombing runs, blockades or any of this other nonsnese; they'd probably come up with a way to induce all of their rifles to self-destruct and then send in Doctor Jones to steal the passwords to their bank accounts.
You can kill a man with a scalpel, but you can't perform surgery with a with a battleaxe.
I really liked the Vengeance as it was an understandable response to the loss of Vulcan
It was an OVERREACTION to the loss of Vulcan, which Kirk made pretty clear in his speech. The film wasn't particularly subtle about that point; both Vengeance and Marcus represented a new direction for Starfleet that was utterly wrong in almost every possible way.
Starfleet had it right the first time, and the Enterprise represents that better than anything else.
