If it's only for one city (Schweinfurt), that's not that useful to be "critical." Now, you make it every city produces two trains (kind of like Regensburg allows every city to produce two 109s), and you have a compelling reason to launch repeated attacks as the Allies. However, it may also imbalance things more than we want since one could effectively double Germany's industrial buildup.
Another option would be to either reduce the build cost of German flak artillery, which (I think) is easier than the improvements because only Germany has access to them? That would be useful to Germany and potentially a decent reason for the Allies to attack it? Maybe a 25% reduction in cost across the board?
Reducing the cost of flak artillery is doable, and could be useful. However, that could lead to a situation where the German player is desperately trying
not to finish flak since next turn, the cost will be reduced. (E.g. see that flak will be completed next turn, switch to train, which will not be completed, Restore Schweinfurt, switch back to flak, have more shields than if Flak were just built.)
How about an extra reaction (or two) per turn for each unit. I think that would be fairly easy. Think better ball-bearings, better equipment, less maintenance. Or, maybe, recover all German units by 2hp per turn or something. Think better industry, easier availability of replacement parts.
Can you please define, "really good success?" They basically start as non-veteran to help balance 250lb bombs but I suppose I overlooked what might happen when the 500lb show up. Maybe I need to make deeper targets start as vets and just leave a few of the more local targets non-vet to account for this? I would not need a script - this would be something I'd want to manually change on a case by case basis and simply haven't considered. I do think we might want new industries built to start as vet given you've mentioned this.
3 vet 500lb bombs stand a pretty good chance of destroying a target. This was most noticeable with Lancasters vs Urban at night, but there were probably daytime cases as well (using B24s) that don't stand out as clearly. This would certainly explain some variance I saw. Had I noticed the lack of vet status before, I would have started my assaults with Vet B24s, to try to get the most out of the first few attacks (each attack has a 50% chance for the defender to become veteran). What I typically did was to send in rookie B17s (when I had mixed attacking forces) to soak up reactions (and possibly get damaged and become vet).
A quick test of 4 vet 500lb bombs vs rookie industry (4 Aircraft factories, 2 Refineries) had 4 of the 6 targets destroyed.
I checked, and new targets are veteran.
If we want a few soft targets, why don't we just pick a few locations, and have the units at those locations be set to half health (or less, if they were already damaged) each turn, at least until they have been destroyed once. That way, there isn't pressure to search the starting map for the weak targets and then remember where they are in the current game.