I would go for something less rules heavy. Too many special rules could result in "oops i forgot that, sry" - situations. But i like the general concept. here are my thoughts:
Base size - makes sense. And because it is part of the model, there are no rules people have to keep in mind.
no new headings/burn retros and limited AAF:
While i understand the motivation behind this (making it even less mobile than a battleship), i don't think it is realistic. If it is possible to get a positive accelaration, it should be technically possible to get a negative accelaration, too. Both orders should be allowed, or not allowed, everything else would be a construction-related issue for each individual vessel (why should all ships of this class be equiped with additional thrusters to accelerate faster, but without retro-thruster to accelerate in the opposite direction, when the technology behind this es exactly the same?).
ramming:
if there is a damage bonus because of the ships mass, it should be caused because of the mass. More Hitpoints = more ramming damage. No need for special rules!
reload repeat:
The "double = out of ordnance" rule is outdated, so the risk of running out of ordnance should not be an issue...And a reload or something similar would make it "more easy" to reload, and that would not make sense as a general trait for a ship type. No need for special rules here.
If you are using some kind of "out of ordnance" houserule: just make this class an execption to that rule.
shooting:
This rule would only benefit weapon batteries. I would increase the weapon range instead, combined with "more weapons than a battleship" - this is the way the rules are written for the existing classes (bigger firing platform = more range). A rule which could get droped, and since range would be in the ships profile, there would be no special rule people have to remember.
Being shoot at:
I would just give the enemy weapon batteries a left collum shift. This is an easy to aply rule, and since the ship is a bigger target, no matter of abeam or moving away etc., there should be a benefit in all situations.
explosion:
Makes sense.
victory:
Disengage-Bonus doesn't make sense for me: Disengaging per roll (not by flying from the table edge) means the shut-down of all systems, so the ship can't be seen on tracking devices/scanning systems etc. -> Disengaging this way should be either the same as for all other ships, or it should be even more difficult for a dreadnought.
Making it more easy to hide this ship from enemy scanning systems would be against realism ("(...) their energy signature is like a sun to even the least advance tracking system").
Shooting the hulk doesn't make sense to me: If this ship is that valuable, why should you destroy the chance of getting it back some how? And when even the 08/15 lunar cruiser is considered a sacred vessel, wouldn't it be a sacrileg to destroy a vessel even more sacred than an imperial battleship? Mechanicus can shoot their own hulks because they are using experimental equipment, and they value their knowledge about anything else; there is no other faction at this moment which is able to shoot at their own hulks, even if denying technology could be good reason for doing so (not even necrons or eldar). I think this behavior should be reserved for mechanicus. I am sure an admiral who gives the order to destroy the hulk of a sacred imperial dreadnought should be purged for heresy after the battle.
+25% victory points:
Seems to be ok. I am not sure if this is needed. it would only have an effect if the ship actualy end up as a floating hulk, and the destruction alone should be worth a lot of points. it would be a rule that would be used only in rare situations, and would be forgotten easy. Maybe the +25% should be even awarded if the ship is destroyed, no matter if it would end up as a hulk. This would give the user another reason for disengaging before the ship suffers too much damage. And when a ship of this size goes down, the chance of finding large parts of the wreckage should be quite high - and even if nothing can be salvaged: It is unlikely that this ship can get replaced.
One more suggestion: Maybe something extra relating campaign games. There should be no auto-replacement for a ship like this.
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to summarize: i would go for:
A Dreadnought uses Battleship rules, with the following exeptions:
- 80mm Base
- no burn retros or AAF special orders (making it even more clumsy that battleships)
- Dreadnoughts suffer an additional left collum shift if fired at on the gunnery table
- catastrophic damage radius is increased by 2d6
- grants +25% victory points if destroyed
- campaign only: no auto-replace in a campaign
This would mean:
The only rules the players have to remember during each turn: no burn retros or AAF, 1 collum shift if fired at
The rules the players have to remember when the ship gets destroyed: +2d6 explosion radius, +25% victory points
And thats it.
I think this ruleset should be able to represent Dreadnought-sized vessels, while the actual rules used are as simple as possible.
Edit: This ruleset would even be small enough you could just write it in the ships profile as a reminder (like the "no come to new heading" sentence in every battleship profile (excluding fast battleship class).
