The Federation are in a somewhat enviable position with respect to their Heavy War Destroyer as it is itself modular in its construction. Virtually any variant of the DW could conceivably be built with the HDW secondary hull mounted in place of the ventral warp nacelle. What I am proposing is that the Federation build Heavy Mobile Carriers: essentially HDWs constructed using DWV hulls rather than DW hulls.

The ships would make exceptional small carriers, carrying up to 18 fighters, with all options configured as shuttles with ready racks. Furthermore, they could even be configured as "pocket" control ships with a full squadron of heavy fighters in semi-external bays.

I do not see this as being a precedent for creating a new line of variants as most empires would not have as easy a time of converting their HDWs into heavier carriers or applying the HDW systems to their Mobile Carriers. (Well, maybe the Lyrans could do it. Their HDW design is pretty modular, too. Although, I doubt the Lyrans would really bother as they are not as much of a fighter using empire.)