Hmm... don't we already have a low tech multipurpose frigate? The lasher comes to mind, with its many variants.
@Gothars, I doubt that a low tech ship would have phase coils, its pretty lore breaking. I agree with the augmented hound theory.
@Alex, What will the small, previously unused midline frigate do? The midline epoch ships are already kinda weak compared to the mastery and expansion stuff. They can't take as much of a beating, and don't have a lot of offesnive capabilites. For example, the Eagle could actually have a large mount for its center medium hardpoint.
I also think that the midline era could use a different frigate, one that isn't slow (brawler) or optimized for support and PD (viligence).