Thanks The WelshPirate
and welcome to the board!
Interesting thoughts... I like the idea of the Hecla having a less than glamourous, work-horse type, role. Would the smaller nacelles really effect speed? I guess it's all depends on how you reckon warp drive works. Perhaps, larger or more numerous reactors would overcome the disadvantage of the shorter nacelles, allowing the ship the power to reach high speeds, but not maintain them for as long. With a role keeping her in or close to Federation space, with short mission durations, this wouldn't be much of a disadvantage.
Yeah, I'm not sure how much nacelle length affects their speed. But looking at the Enterprise, half of the nacelle sticks out past the aft most point of the ship proper, and that alone makes up for a good 1/4 of the entire length of the ship.
They gave the Constitution-Class engines that long for a reason. And whatever advantage that is, I would assume the Helca makes due without judging from how much smaller it's nacelles are compared to the ship's length.
But anyway, something about the ship makes me think it's more of a support ship than a battle ship. I always thought of the Miranda-Class as Starfleet's go-to destroyer.