OK, these are all good comments. I'm going to try something that ends up hopefully satisfying everybody (yeah, I know). We'll try it for logistics after the game on May 14th (which is the last Dark Caste mission) and get people's opinion's then, and then given that feedback we'll finalize something for the remainder of the campaign.
Mech, ASF, and Vehicle Repair Errata v1Condition 1: 30 points or less of JUST armor damage - 5 WCP to repair
Condition 2: 31+ armor, or ANY form of internal damage (structure, equipment, etc), but not "crippled" as per TW - 1/2 tonnage in WCP to repair (round up)
Condition 3: Crippled as per TW definition, but not destroyed** - tonnage in WCP to repair
Condition 4: Destroyed (any result that qualifies as a mission kill**, including CT IS destruction and triple engine hits) - 25+tonnage in WCP, or you may replace the unit using normal replacement rules (50+new unit tonnage in WCP)
Let me sum up what this does, because there is some give and take here.
Give: Repairing minor damage becomes MUCH easier, without having to do a great deal of bubble-counting (if we want to count bubbles, we could run a full AccounTech merc campaign after this one ends...). This should also somewhat de-incentivise spreading around damage *just* to screw players (I've witnessed a fair number of secondary-target ML shots against pristine Mechs just to cost WCP). 30 damage generally requires more than just a desultory amount of fire during the last turn of the game. This should also INCENTIVISE Clan players to weigh Forced (or Voluntary) Withdrawal very heavily, because it will preserve a good lot of WCP to keep a unit from being totally destroyed, which now is much easier. Do recall that the Clans are all about minimizing waste...
Take: Classifying a unit as "destroyed" is now WAY easier to do; whereas before it was immensely rare (technically, the only way to *completely* destroy a Mech is to kill all of the CT IS, but between CASE and lack of OPFOR HE damage, it becomes nearly a pointless classification; almost all units die to stuff like engine hits). This should be VERY easy for everyone to remember what "kills" a unit; if damage removes the Mech from the initiative order, it's counted as "destroyed".
It is technically possible to have a headshot on an otherwise pristine Mech which qualifies the unit as "totally destroyed", but weighing the rarity of that event against how common it'll be to save a ton of WCP from the minor damage levels, I feel confident that this will more than balance out in player's favor in the long term. There is a single exception to Condition 4.
**EXCEPTION: If the crew EJECTS from or ABANDONS the unit, dies from accumulated crew hits, or withdrawals from the game board, it is removed from the initiative order but does not enter Condition 4. The actual damage to the unit determines the Condition Level.
Finally, I want to address this:
As an OPFOR player, you are supposed to play to win. If that means hitting mechs and all you do is armor damage, so be it. All damage costs WP to repair. Those are the hazards of winning the bid.
As an OPFOR player, you ARE in fact supposed to play to win. You should be playing as best as you can to win the SCENARIO and achieve your stated objectives. I want the OPFOR to be trying their very best to achieve their in-scenario objectives, or to deny the PCs their in-scenario objectives, during every single game. However, almost never will that include firing a single IS ML at an undamaged Assault Mech as a secondary target while actually *saying*, "I'm just shooting this to force you to spend WCP." Playing to win the metagame is not one of the OPFOR goals at this time. Attacking with the sole goal to hurt a PC in their WCP is playing the metagame, not the board game.
There is no way I can be inside the OPFOR's actual heads. I cannot know whether you're firing that single weapon at Unit A because everything else on the board is focus-firing Unit B and that's all you have that can reach them, you're planning to hammer Unit A next turn, and you just ran out of time/turns. I also cannot know whether you're firing that single weapon at Unit A because you have no actual hope of hurting the unit and are instead just trying to cost the player WCP (which is an out-of-game concept that the OPFOR should have no knowledge of). I have to trust that each of you are leaning more towards the first example, rather than the second. If you're legitimately shooting up several Mechs and all you do is armor damage, that's the game. If your INTENT is to screw the PC out of WCP, then you're in the wrong.