You do realize that the Retribution, before the decision to make it FP18@45cm, is FP12@60cm? The Retribution at FP18@45 cm won't really outgun the Invincible if the Invincible is at FP15@60cm. As I pointed out the difference is 2 dice in the approach and moving away profile and 1 dice only in the abeam profile.
And I STRONGLY DON'T. I don't want a ship with 3 disadvantages which will then cost almost as much as a Retribution because the weapons will be bumped to FP15 (Smotherman puts it at 342). You're going to spend that much points on one ship that will might just blow up the first hit it gets after the shields have been taken down because it rolls a 5+ on a crit and a 10-12 on the crit table? I don't think a battleship should be like that. In this regard, I retract my statement about poor Retribution but only in the sense that no one would ever want to take your iteration of the Invincible if only because it will blow up faster even though it will perform at par with the Retribution.
There is no official precedent yes about ships having less HP on one hull, but experimentally, when this ship came out in the BFG Mag and Annual it broke that precedent so the HA were thinking it was possible.
Again, toughness is a measure of the physical ship itself. Internal structure and armor would be the real life references. Since we are talking about space ships, then shields would be included and these are already lowered. You don't want to touch the armor however as this actually would be the one needing change. Fine. Therefore the HP should also be lower than a typical battleship. Lowering the HP would also justify it getting 25 cm speed. With 12 HP I can't see it happening even with reduced shielding because I think the energy saved won't be enough to add that much speed since the mass because of the structure and armor remain the same as a normal battleship.
However, you want it to have 12 in the expectation that lower shields and penalizing a ship with 2 types of crits would balance it out. I'd rather take HP10 and only 1 crit disadvantage along with the lesser shields. And as I said, I even feel 2 shields were extreme. It should have 3.
Invincible (Smotherman puts this at 315)
Type Battleship
HP 10
Armor 6+/5+
Shields 3
Turrets 4
Speed 25 cm
Armament
Dorsal Lances Str 3@60cm
Port/Starboard WB FP12@60cm
Prow Torps Str 6
Choose penalty from:
1. Roll 2D6 per hit to check for crits or
2. Crits on 5+ instead of 6 or
3. +1 Modifier to crits rolled in the Critical Hits Table.
Tough but not as tough and not easily taken down but still can be one shotted in the right circumstances and something which can be taken and reasonably expect to survive.
No.
FP12 is unacceptably low for a true battlecruiser. It SHOULD be of the standard of a Retribution. So what if it's only 1 or 2 dice less? Good!
The smotherman value is off for several reasons:
#1. it significantly over-values R60 over R45. It's a 33% range increase, but a 50% cost increase. That easily accounts for 15pts of difference. It also doesn't account for use - Retribution is going to have a good chance of using that off-side firepower, whilst Invincible's will mostly go to waste. Assuming 50% as much usage of the off-side, that drops Invincible sub-300pts. Now you have the drawbacks on top of that.
Now I'm not advocating that Invincible should be less than 300pts, merely pointing out the limitations of Smotherman. 320pts would be a good
starting point for negotiations on its price.
Historical battlecruisers sacrificed protection for their speed, not size or firepower. In BFG, protection is given by shields and armour. The shields are massively reduced. The external armour can't be reduced without it not being an IN vessel, so we reduce the internal armour by applying special rules to represent inadequate bulkheads. Both of these easily cover the reduced mass and increased power required for the additional speed. It should be 12 hits because of its size, and 2 shields and 1 special rule will represent teh increased vulnerability.
Inadequate Bulkheads: The Invincible Class Heavy Battlecruiser was designed without many internal bulkheads in exchange for its speed. This greatly increases its susceptability to critical hits: Critical Hits against an invincible Class Heavy Battlecruiser are normally scored on a 5+ instead of the usual 6+; In addition, all rolls on the critical hit chart gain a +1 modifier.
As for battlecruisers taking a critical hit and blowing up:
HMS Hood took a critical hit and blew up.
HMS Invincible took a critical hit and blew up.
HMS Indefatigable took a critical hit and blew up.
HMS Queen Mary took a critical hit and blew up.
HMS Lion was only saved from a critical hit to Q turret by prompt DC action: a fire spread that would have detonated Q Magazine had it not been immediately flooded.
Only one UK battlecruiser sank from attrition, the Repulse, which was bombed and torpedoed multiple times.
SMS Lutzow was caused to sink by a critical hit that caused flooding.
No other German battlecruisers were sunk.
No Russian/Japanese battlecruisers were sunk (Save Kongo and Haruna, which had been rebuilt as battleships).
So overwhelmingly, battlecruisers were lost to critical hits!