[GZG] FT:XD changes, part 2/2

Here's the second and last set of ideas for FT:XD revision 1.1. In the
interest of finishing this revision no more than two months later than I'd
planned, I'm going to leave out the new "cinematic vector" movement system and
Yet Another rewrite of the fighter & point defence system.

* Kinetic fighters. These are a variation of attack fighters that use missiles
or other kinetic projectile weapons instead of beams, so ignore standard
screens. Like attack fighters, they don't do well in dogfights but
get +1 attacking ships.

Projectile weapons in FT don't re-roll when attacking ships, and
neither do the Kra'Vak fighters with kinetic weapons in FB2. I'm inclined to
think that ignoring screens is more valuable than not
re-rolling, so the points cost should be 5 per fighter rather than 4.

* Shell armour. (OK, not a new idea at all.) AKA layered armour, as used by
Phalons in FB2, that absorbs half damage per layer until you get to the hull.

Unlike some of the alien systems, it's a simple extension of the existing
armour rules. It could be useful for modelling any other
race/fleet that relies on multiple layers of armour or force fields,
not just Phalons. Heck, I wouldn't be upset if some of the NSL ships in FB1
were redesigned with shell armour.

* Precision fire controls (optional) A PFC is a fire control that allows
standard ship to ship weapons to target specific systems on an enemy ship,
similar to needle beams. Mass 2, points cost 8.

Each PFC carried allows one ship weapon to be fired at a nominated system on
an enemy ship within range and firing arc. Instead of normal damage, roll a
single D6. On a 6 the system is knocked out as if hit by a needle weapon.

Precision fire is carried out AFTER all other weapons fire by the same ship:
ie you can't knock out a screen first and then fire the rest of your weaponry
on an unscreened target. Of course, your other ships can...

* Engine overloading (optional) After writing orders, placing missiles, and
moving fighters, but before ships are moved, player has option to order an
engine overload.

Roll a D6. The result is used for two outcomes.

First, it is the number of extra thrust points available for this turn only,
up to the maximum of the current main drive. (ie a ship with main drive 2 can
never add more than 2 thrust points by overloading.) In cinematic movement
this extra thrust can only be used to increase or decrease velocity, not to
turn more than normal.

Second, is is a threshold check for the main drive, taking into account any
current hull damage. If the roll equals or exceeds the threshold point, the
main drive is damaged at the end of the movement phase. Yes, ships with main
drive 6 or more can simultaneously gain 6 thrust points for the turn and burn
out their engine in doing so.

This represents the ability of exceptional captains and crew to
perform miraculous-seeming manoeuvres, so is definitely optional.

If you decide to allow engine overloads in one-off battles rather
than campaigns or roleplaying scenarios, engine overloads should be allowed no
more than once per player.

OR, each attempt after the first by any ship belonging to the same player
reduces the threshold check by an extra 1, so the second
undamaged ship fails on 5+, the third on 4+, and so on. No ship can
attempt an engine overload if failure would be automatic.