5.8c for the J/Y-class transports vs 27c for Warp 3, but that's still a year at warp 3 to get from Sol to the most distant Earth colony. I don't think any amount of sprint is going to matter at these slow speeds. On the other hand a higher cruise pays dividends pretty quickly since you can sustain it for days, weeks or months.We don't need extra cruise speed in the short-term, if this is meant for escorting crappy Boomer freighters. Warp 3 already outpaces them significantly, Warp 3.2 is overkill.
These things need maximum dash speed to get from wherever they are to a distress call ASAP.
[X] Horizontal Axis Nacelles (+0.4 Maximum Warp Factor)
Faster cruise speed would make it easier to establish escort relays for the J/Y-types, where each year the escorts cycle out.
A dozen is ambitious! My point is that when a major power pokes their nose in, there's not much we can do. They've got Shields, Photon Torpedoes advanced beam weapons and such. Pirates operating in our trade lanes are far more our speed and given that even at Warp 3 it's almost a year from Earth to the most distant colony, a high cruise is more likely to benefit us in that role.I don't think the Klingons are a major issue right now, they're on the far side of Andorian and Vulcan space as far as I'm aware. And I think there are some other more minor powers in between too. At most we might get one or two ships off on their own as pirates or adventurers looking for glory.
Massing a dozen or so of these in the Sol system should probably be enough to stop one ship from the klingons.