Ok, first off, this is about as ALPHA-stage as it can get.
So, we have the "Punisher" class cruiser in the Additional Ships Compendium... but I don't like it, mostly because it's got too much going on, and feels like an Adeptus Astartes strike cruiser on steroids. Conceptually, what I'm looking to create here are one or more light cruisers who wouldn't necessarily be standard fleet assets, but possibly something you could include for fun in a larger fleet action centered around a planet.
So, while I was waiting for my basecoat to dry on the Blasphemer-class, I went leafing through my copy of Matthew Farrer's Enforcer and my Dark Heresy Book of Judgment for inspiration. In terms of background or general rules, I'd offer the following. Adeptus Arbites ships should either come out of a Planetary Defenses points allotment, or if bought as part of a fleet should not count toward the requirements for CBs, CGs, or BBs as the Adeptus Arbites are fully outside the Imperial Naval hierarchy and operate separately (furthermore, are only able to squadron with other Adeptus Arbites vessels). I don't think they should be able to take secondary commanders from their "parent" fleet, nor should they really get an admiral-level commander of their own unless you're doing a custom scenario anyhow, IMO.
So, the Adeptus Arbites are by nature primarily a dirt-side force, but they do maintain small fleets of patrol boats and monitors for anti-piracy and customs work (getting a lot of this from Enforcer). Each Arbites cruiser is essentially a space-going Precinct House, complete with holding cells, at least one circuit-riding Judge, Verispex officers for investigations, and of course, a full complement of Arbites troopers trained not only in riot control but also in boarding actions. There's an excellent sequence in Crossfire (the first book of the Enforcer trilogy) where an Arbites Indictor-class Fast Cruiser's troops complement storms an Ecclesiarchy pilgrim transport. We don't get to see much of the Indictor's actual armament (at all), sadly, but the name alone conjures up images of a nimble light cruiser used for pursuit and capture missions.
So, I'm playing around with the Smotherman v205 document, at least to get myself started.
Arbites Indictor-class Fast Cruiser
Type/Hits: Cruiser/4
Speed: 25cm
Turns: 90*
Shields: 1
Armor: 5+
Turrets: 1
Port Weapons Battery - 30cm - Str 4 - Left
Stbd. Weapons Battery - 30cm - Str 4 - Right
Prow Weapons Battery - 30cm - Str 2 - L/F/R
Special Rules: Improved Thrusters (+1D6 AAF); Arbites Precinct House - gets +1 to its dice roll when defending against boarding actions.
So, adding things up, it would be 20 points for the hull, +5 points for the speed, +10 for the shield, +10 for the hull, +5 for the turret, +12 for the port/stbd batteries, +3 for the prow batteries, +10 for the improved thrusters, and I'm going to add +5 points in for the Voss-pattern defensive bonus, for a total of 80pts. I have -NO- idea how to properly value the defensive bonus, so totally let me know if that's off.
My thinking: This is basically a weaker, cheaper Siluria, mostly because I (a) didn't want to simply port the Siluria over and buff it, (b) like the idea of adding some even smaller light cruisers to the game, and Arbites patrol ships seemed like a good place to do that, and (c) I don't want the kind of crazy power creep for these guys that the Punisher-class has. They're customs cops who primarily deal with escort-level transports and pirate raiders, so they really don't need SERIOUSLY STRONG cruiser-level stuff.
The other idea I had was, well, I'll be honest, a slightly modified Defiant-class:
Arbites Sentencer-class Customs Cruiser
Type/Hits: Cruiser/6
Speed: 25cm
Turns: 90*
Shields: 1
Armor: 5+
Turrets: 2
Port Launch Bays - 30cm - Str 1 (Fighters & Assault Boats) - N/A
Stbd. Launch Bays - 30cm - Str 1 (Fighters & Assault Boats) - N/A
Prow Weapons Battery - 30cm - Str 4 - L/F/R
Special Rules: Arbites Precinct House - gets +1 to its dice roll when defending against boarding actions.
So, since I'm pretty much porting the Defiant over, I figure 110 points would be acceptable hopefully. My big modifications are twofold: torpedoes are a naval weapon and these guys really only need defensive batteries, and I don't see the Arbites using bombers but I do see them possibly using something like a light ketch to perform longer-distance ship inspections, so that could translate over to assault boats pretty easily (and I figure trading out bombers for assault boats is an acceptable 1:1 trade?). My thinking is, this ship class would be 0-1, or maybe you must take 2-3 Indictors to unlock 1 Sentencer.
I did think about trying to combine the two cruiser styles, but every time I did, I basically ended up with something very similar to the Punisher that had simply too many little toys built in to be effective at any one role, and for that matter, fielding more than one Arbites cruiser would have meant generating a significant amount of extra attack craft for an Imperial allied fleet. I'd rather have a couple of Indictor-class gunships and maybe a single Sentencer-class if an engagement was really big enough to warrant it (otherwise, these are really meant for special scenarios, or for an alternative approach to a convoy or pirate base raid).
Why a light carrier? I figure it's moderately fitting the lore for them to have extremely limited carrier assets to help them police larger ports (sending out small customs boats to run inspections while stuff's still on its way in from the transition point), and they might keep some limited interceptors onboard as well to handle torpedo-armed pirate raiders. My thinking is, a big Sector capital like Port Maw would only have maybe one or two Sentencers and a handful of Indictors, backed up by perhaps a squadron or two of escorts similar to Defense Monitors, and really most of the cruiser assets would probably be "riding circuit" throughout the Sector, bringing Judges to far-flung worlds that don't have their own Arbites Precincts, or tasked out to provide coverage for smaller mercantile ports in other systems on a rotating basis anyhow.
If I were to add any other rules, I'd say Arbites ships should use the Imperial Navy Leadership Chart for rolling ship leadership rather than going with the standard Defense Ld 7 (and possibly this too for Arbites-controlled Defense Monitors, although I don't like the idea of giving the Arbites lances at all and the Navy probably wouldn't either), and since they're professional riot cops, should they get the +1 boarding modifier like Orks and Chaos? I'm just thinking of squads of riot shield & shock maul guys storming a hull breach, backed up by ranks of shotgun troops and boltgun-armed sharpshooters and grenade launchers, with grapplehawks and cyber-mastiffs charging breaking up organized defenses... these aren't exactly press-ganged naval ratings!
Questions? Comments? Suggestions? Improvements?