Both of which are boring. Vector movement is extremely predictable. It makes for a slow circle of death as you fly in at high speed and then start turning in to face your opponent and they do the same - then you spiral towards each other. It's meh at best and downright annoying at worst. Cinematic movement is actually fun.
I'm going to throw this down here- page 31, core rules
While there's no point where the rules specifically tell you you cannot take say a cruiser squadron of three Isonades and a Ladon, the way the squad minimums and maximums in the profiles are written implies that the squad is chosen by ship type, filled out with that ship type, and then exceptions might be applied. If accompaniments are bought as squadrons with modified sizes, then no. The process would be pick the squadron type from all possible Escort types, then fill out that squadron, and then count it as part of the lead ship's squadron.
As for a why not, I agree that it probably wouldn't be gamebreaking, yeah? But it would also be that much more to keep track of. Now I know Terran players will yell at me because it just plain doesn't happen, I know the Terran Heavy doesn't mesh with their standard Cruisers, but there's an entirely possible squad of two Cruisers led by a Heavy and accompanied by a Shield Cruiser. That's three ship types in one squad, and though the Heavy contributes to this by not being a team player, you've got to imagine how awkward that squad could be even if the Heavy meshed well with its standard counterparts. Three different weapon loadouts, three different defensive profiles... There's nothing broken about it, but its just that much more of a hassle, particularly when one of the big recurring complaints about FSA is the math of linking, and when taken in context I think there's a reason why with this exception you don't see a bunch of squads able to take more than two varieties of ship. This is of course just my thoughts on the topic- I was surprised not to see something in the FAQ about squads of the same class but different profiles, but hey, I guess that didn't really get to come up until System Wars and Taskforce added some alternatives.