I actually think access to CVLs and ECVs will make IN LESS of an AC fleet, because the ability to take a cheap and almost totally defensive carrier will free up the obligation to take an offensive carrier, freeing up points for gunships.
Also, the reason the Despoiler is more expensive than the Emperor is because it has 30-40% more firepower, more speed, ability to turn under fire, and free assault boats, with the Emperor's only bonus the +1Ld. I personally think the assault boat upgrade is worth 10pts on an 8LB ship, and the Emperor gets them too cheaply.
If the Leadership is worth 25pts, that makes the despoiler 35pts more expensive than the Emperor for +30% firepower, +5cm speed, and ability to turn under fire. If the speed/ability to turn are worth just 15pts, that makes the Despoiler's additional firepower worth 20pts, which I think is fair. I could see a further 5pt reduction, but that's it.
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We do need to talk about the Relictor though. The fluff talks about it being faster than a Desolator, which it's only barely, the weapons reduction is comical compared to the bare increase in speed, and S3 Lances feel weirder than overpowered weapons batteries would be because they're more WYSIWYG. Rather than use the Scartix coil as justification for a pathetic increase in speed, or make it cheaper and thus impinge on the Desolator, I'd go with the following:
"The Relictor class battleship was first developed during the Great Crusade under the supervision of Arch Magos Eneatu who theorised he could gain even more performance from the Desolator's engines. Unfortunately due to the increased power demands of the improved engines, the Desolator's high power lances had to be exchanged for less power hungry weapons systems. Few were ever created following Eneatu's designs, and most were assigned to the various space marine legions that went traitor before the Istvaan incident.
The Relictor in its current form is believed to have been born when the heretic captain [insert fluff-appropriate name] encountered the dark-age space hulk [insert fluff appropriate name] in [insert fluff appropriate date]. It is unknown exactly what he discovered as the hulk disappeared back into the warp soon after, but since that date various Relictors have surprised Imperial vessels with implausibly powerful broadsides.
The most famous Relictor is the Harbinger, recorded as the head of...etc"
Relictor class Battleship, 360pts.
Prow S9 Torps
Dorsal FP9 WBs@60cm
L/R Lances S2@45cm
L/R WBs S18@30cm
The Relictor is Massive and has Improved Thrusters. The original designs used less powerful, longer-ranged weapon batteries. The Relictor may revert to this pattern by exchanging its FP18WBs for FP12 versions with 45cm range for -20pts.
This way it stands up pretty well to an Imperial Retribution.