BS:4 Armour 14/14/13 HP:27 Save:6++
Unit Type: Super-Heavy Vehicle

Wargear:
Melta Cannon (front right tower) (72" S:10 AP:1 Ordnance 1, Apocalyptic Blast, Melta)
Inferno Gun (front left tower) (Hellstorm S:7 AP:3 Primary Weapon 1)
Vulcan Mega-Bolter (main tower) (60" S:6 AP:3 Heavy 15)
Vortex Missile Battery (Range:Infinite S: D AP:1 Ordnance 1, Large Blast, Vortex)
7 Void Shields

Rites of Repair
The Battle Chapel requires extensive onboard workshops to keep itself functioning. During battle, these specialists may attempt to repair an embarked vehicle or even the Battle Chapel itself, though the latter is a much more daunting challenge.
Once per turn, during the Shooting Phase, you may attempt to repair one vehicle embarked on the Battle Chapel. On a roll of 2+, restore one Hull Point, one weapon lost to a Weapon Destroyed result, or undo an Immobilized result. The repaired vehicle may not disembark until the next turn.
Alternatively, you may instead attempt to repair the Battle Chapel itself. On a roll of 5+, restore one Hull Point.

Siege Towers
The Battle Chapel's forward towers providing not only firing platforms but boarding ramps to attack the upper levels of fortifications.
Infantry models transported by the Battle Chapel may disembark directly onto any level of a ruin or building within 6" of the Chapel's front, including battlements.

Samsonic Ram:
The Battle Chapel's front steps are in fact are massively reinforced ram designed to shatter the base of a fortification's wall with a blast of sonic vibration.
Any building or immobile structure that is rammed by the Battle Chapel and takes a penetrating hit loses 1D3 Hull Points instead of one.
Further, when ramming a building or immobile structure, the Battle Chapel gains the Wrecker special rule:
Wrecker: Weapons and attacks with this special rule may reroll failed Armour Penetration rolls against fortifications and immobile structures (such as bunkers and barricades), and add +1 to any result rolled on the Building Damage chart. If this attack damages a bulkhead or wall section of terrain and destroys it, remove that section of terrain from play if possible.


Special Rules:
Assault Vehicle

Awe-Inspiring:
Songs of praise and pealing bells ring out from the Battle Chapel, clearly audible over the roar of battle, while its icons loom sternly over the fray.
All friendly units within 12" of the Battle Chapel re-roll failed Morale, Fear, Pinning tests, and Act of Faith tests, and gain the War Hymns special rule. However, they may only use the "The Emperor Protects" and "Righteousness of the Emperor" hymns.

Auspex Maximus:
The Battle Chapel's highest tower bristles with arcane sacramental sensors that can detect enemies. Thus guided and installed on an elaborate swiveling mount, the Adventus's Vulcan Mega-Bolter can engage enemy fliers and ground troops alike.
At the start of each Shooting Phase, the owning player may give the Battle Chapel's Vulcan Mega-Bolter the Skyfire special rule for that phase.

Holy Light:
As the massive war machine crashes into the enemy lines, its gilded armour gleaming and its sacramental spotlights blazing, the eyes of the evildoers are dazzled by a pure white light and their ears fill with celestial music. Then the faithful charge out of the vehicle and rip them apart.
When a unit charges out of a transport with Holy Light, it counts as having assault grenades and inflicts a Blind attack on all enemies it is charging, resolved at Initiative 10.

Ponderous Beyond Belief:
More a mobile building than a vehicle, the Battle Chapel has tremendous trouble maneuvering -- but then it rarely has to.
During its Movement phase, the Battle Chapel may either move 6" directly forward or pivot up to 45 degrees, but not both. The Chapel may never move in the Shooting phase.

Reactor Meltdown
If the Battle Chapel suffers a Titanic Explosion! result on the Catastrophic Damage table, its plasma reactor goes nuclear! All hits from this Titanic Explosion! are resolved
as being from a Destroyer weapon.

Transport:
Transport capacity: The Battle Chapel may carry models on two levels, which are treated separately:
The Galleries may carry 50 infantry models and provide 50 fire points: 15 on each side, 10 front, and 10 rear.
The Nave may carry 100 models, including Bulky, Very Bulky, and Extremely Bulky models. In addition, it may carry smaller vehicles, including other super-heavy vehicles, which take up 10 models' worth of room per Hull Point. Vehicles that are transports may carry models inside without taking up additional room in the Battle Chapel.
Fire Points: 15 on each side, 10 front, and 10 rear.
Access points: One at the front and one on each side.

Vortex Missile Battery:
The Battle Chapel may fire a maximum of seven vortex missiles over the course of the battle. No more than one missile may be fired per Shooting phase.
When the Battle Chapel suffers Catastrophic Damage, roll one dice for each remaining vortex missile. On a roll of 1-2, the missile explodes. Place the vortex’s blast marker on the centre of Battle Chapel, and then scatter it 2D6".


Options:
May add up to three secondary gun mounts (one per tower), each armed with one of the following:
- Exorcist Missile Launcher: 65 points
- Flamestorm Cannon and twin-linked heavy bolter: 50 points
- Magna-Melta (Range 18" S:8 AP:1 Heavy 1, Large Blast (5"), Melta): 70 points
-Avenger Bolt Cannon (Range 36" S:6 AP:3 Heavy 7): 50 points

I'm relying mainly on Ovion's costing method but scaling everything up, typically x9, for one of the heaviest of super-heavy vehicles.

Start with Reaver Titan (1,450 points)
Armed w/ Melta Cannon, Inferno Gun, Vulcan Mega-Bolter (not a legit load out since it's one arm weapon and two carapace instead of the other way around, but since none of these is a D weapon it's not abusive)

Downgrade Super-Heavy Walker (100 pts per Ovion) to Super-Heavy Vehicle (60 pts): -40
Ponderous Beyond Belief: -90
TOTAL SUBTRACTIONS: -130

Add Shield of Faith, which is 5 pts on a Rhino or Immolator a fraction of the size: +90
Assault Vehicle, 10 points on a normal vehicle: +90
100 passengers @ 2 pts each (per PM w/ Ovion): +200
50 fire points @ 1 pt each (a guess): +50
VMB gets essentially Tau Velocity Tracker (+20 for all weapons on a single normal vehicle): +40
Awe-Inspiring = Laud Hailer @ 10 points, plus Icons of Courage @ 20 points, plus Kriegsminaret @ 90 points (more than on the Storm Queen because it doesn't take away passenger capacity), +10 because you can't shoot it off like the Kriegsminaret = +130 points
Holy Light = 25 points
1st round ADDITIONS: +625

Adding MORE stuff:
3 extra Void Shields (based on cost of an upgraded Void Shield Generator building): 100 points
Vortex Missile Battery and 9 HP (based on cost & structures compromising Aquila Vortex Missile Strongpoint) : 535 pts
Discard Mighty Bulwark & AV 15 from Vortex Missile strongpoint, as the price of making it mobile: 0?
Repair other vehicles (based on cost of 5 servo-arm servitors): 50 pts
Repair itself (basically Titan-scale It Will Not Die, so 9x10): 90 pts
50 more passengers @ 2 pts each: 100 pts
Siege Tower special rule (at a guess): 50 pts
Samsonic Ram (at a guess): 100 pts
2nd round ADDITIONS: 1,025 pts

1,450 -130 + 625 + 1,025 = 2,970 points. Round up to 3,000 because who are we kidding?