No, you are very, very wrong. In fact I was quite happy to hear that the Prometheus and other Advanced Escorts completely lacked it. Now I can captain one and be happy with the aesthetic of the actual design, which I like, without being saddled with the terrible MVAM idea. At first I was afraid it would act like a pet-summoning ability.
Incidentally, requiring three different warp cores is a silly idea (and even if only one of the components actually had warp drive, each would require an antimatter reactor - essentially a warp core - to power impulse engines, weapons, and shields). In no case would Starfleet's needs not be better met by three smaller ships. In fact, given that Starfleet's exploratory mandate is at least as important as its military mandate, three smaller ships is universally superior to having a ship that splits in three.
I would point out that the klingons at the same tier have the ability to fly a ship that SPAWNS fighters and ships..... this is pretty much the same thing as a multi vector assault, doing it with the promie, would be pretty much the same thing just on a smaller scale..
The saucer section of a Galaxy class only has impulse propulsion. What allows it to separate at warp is extending the warp bubble around both sections until the saucer is clear. After that the the warp bubble around the saucer slowly degrades (from the impulse system doing what it can to keep the bubble) allowing a soft falloff out of warp.
Kinda the same principle for photon torpedoes.
All that comes from the technical manual (which is at home at the moment in case I'm a little off)
As for MVAM and saucer separation, Cryptic tried it and couldn't make it work correctly...so they scrapped it early on and put their (limited) resources into other things. They might bring it back later on when they have the resources to do so however
The way to do MVAM in my opinion is to not have it as a player/AIx2 control of the different units over a minute.
I would have it as a swift combat move. You hit the button, your ship splits in three and blasts a target/several targets and then resumes normal form (remember this is actually how it was used in the show.... it wasn't shown as a continual flight of separate modules)
With a bit of thought you could make it work quite cool. For example you could have different effects in operation if you have one of the attack pattern modes running.
Really this seems like a lot more of a viable option now that there is a Galaxy class that can separate. The player controlled section would take a hit to it's shield strength and HP but would gain manuverability and two pets with phasers.
I think it would be pretty awesome, but then I think people would miss it once they were high level and the RA ship is a Defiant class. I don't know though, to me the essence of the Prometheus class was the MVAM and without it I don't want to fly one.
And I still don't see what's supposed to be practical about splitting the firepower and shields of a single ship into three smaller ones. It only makes the individual ships easier to destroy than the entirety, thus depriving you of a whopping 33% firepower every time someone kills one.
I bet they'd sell a bunch of tier 5.5 MVAM Prometheus starships. I imagine it would be a non warp version of photonic fleet or a variant of the saucer seperation mechanic. I don't know if I would get it, but I know several people who would.
Hey, I'm game for a tier 5.5 Prometheus! That was the coolest part of it, though I can definitely see why they didn't do it at first, because the technology and models have to be right for the ships not to look horrible. It takes time to add pieces that look similar and separate in a believable fashion. Also they need to balance the ability, find a way to get it out to the public while making it not seem like a rip-off etc.