Recent thread where I complain about not liking armor facing:
https://www.dakkadakka.com/dakkaforum/posts/list/804347.page
That said, some notes:
Front - All vehicles get +1 T
Sides - All vehicles get -1 T and -1 armor save
Rear - All vehicles get -2 T and -1 armor save
Seems weird that your T values are all either lower or higher than the current T values. Why not just have side values be the current T of vehicles? Not that I think side armor being the current T value is a magic bullet or anything, but it seems odd that you'll always have this gap between side/rear armor values. Like a T7 rhino would have 9/8/6, but no 7.
Also note that this means you'll be making a lot of vehicles T8+. Toughness values 7, 8, and 9 are all significant breaking points. Most common anti-tank weapons are S8, and most medium-quality-lowish-quantity weapons (like autocannons) are S7. So under this proposal, a brightlance would go from reliably wounding a vehicle on a 3+ to only wounding on a 5+ (50% decrease to number of wounds). Plus, a weaker weapon like an autocannon or uncharged plasmagun would be wounding that rhino on the same numbers as the bright lance meaning the lance loses one of its main advantages over those weapons. You could raise the strength values of anti-tank weapons, but then you'll have the side-effect of making things like auto-cannons more effective against T4 infantry.
So heads up. You're dealing with a range of Toughness values that will have a lot of sprawling implications.
Attacker can choose to target the tracks/systems/hover plates... if they do so a successful hit and wound will do a maximum of 1 damage and the vehicle roll 1D6. on a 1,2, or 3 its immobilized. On 4,5,6 no damage/no effect. It makes it risky to blow the tracks off a rhino when you can just as easily kill it
Seems like this would be broken by low-damage weapons. I was already planning to toss some bolter or shuriken cannon shots at your tank. I may as well try to immobilize it and do the same damage as before. Ignoring D1 weapons, it still seems like you'd probably always try to immobilize when using D2 or D3 weapons. Especially if your anti-tank is scattered across multiple units. I'll happily toss plasma pot shots at your melee walker until the 50% chance to immobilize it (effectively taking it out of the fight) kicks in.
Something I've liked the idea of for a long time but haven't actually used:
* Get rid of the vehicle damage brackets.
* The first time a unit with 10+ wounds is reduced to half its starting health or less, it either becomes immobilized (Movement becomes 0" and it can't Advance or Charge for the rest of the game), weapon destroyed (loses a weapon of the attacker's choice for the rest of the game), or stunned (can't move, shoot, or fight until the end of the next player turn).
* Not sure if it would be better to determine which of those 3 happens with a die roll or by letting one of the players choose.
* Could simplify the weapon destroyed result by just changing its
BS to 6+ for the rest of the game. Though this means that things like hell hounds would basically ignore it.
* Could make a stratagem that lets a player choose the damage result to represent the "called shot".
I've also pitched rules for targeting vehicle sub-systems in the past, but those were really meant for things like imperial knights. It might be too much bookkeeping if you had to do it for every tank in the army.
