I'm sorry Steve, but that reasoning just doesn't hold water.
If you've been hit, you've been hit. It's not the equipment rules that need to change, so you can fix your car cheaper, but to correct the behavior and change those rules. But that's a topic for another thread and I don't want to debate it here.
Yes it's an inevitability with this class that contact will happen but if you're so far out of spec after an impact you're replacing control arms, there's always a high likelihood of other things being bent besides just the CAs and you should be considering the subframe for replacement as well. To your example with the porta-power: if you already had the differential out, you're only 14 nuts/bolts & a brake line away from swapping in a spare subframe. You're running in this class and don't have a spare subframe?
I'll be blunt: I can pick up used full rear suspension bits for less than $100 (control arms and subframe), whether those have been in an accident or not is a chance you take in using these but it's not like you're spending $560 for a single set of new CAs only (ignoring the $500+ new subframe cost). You could potentially afford to buy five sets of those used suspension pieces and mix/match to finally find something that works.
Yes it's the same as the parts binning that was done before the head rules.
Yes it's the same as the parts binning that was done before the FPR/CAS rules.
Yes it's the same as the parts binning that was done before the offset bushings.
This is a production car class and there will always be variance in the tolerances of parts and using "parts binning" as a justification to allow a non-stock part is not valid.
Ergo, the need for a slotted UCA allowance in the rules is not supportable on all accounts.
If you can't deem it worthy to spend $100 to fix a bent car then I don't know how to help you any further. I've replaced controls arms many times, and only recently had to replace my subframe after 8 years of driving the car, and not once has this process resulted in my setup guy being unable to get the settings he wants to see. Which I believe are approximately -3.5* or so on each side (static with me in the car).
And for the record, I do all my own mechanical work short of setup, rebuilding of large components (engine, trans, diff), bodywork (paint), or welding so presuming I'm a moneyed player in this game and use a shop for everything, I am not. This position is not something I'm taking to make it more difficult for folks "like you" (as you assert) because I am a guy "like you" doing all my own work when it comes to this except setup. Hell, I don't even have a lift and do all of this on my back with jackstands for chrissakes!
As I've stated before, if anyone has specific, articulable, and sharable knowledge of the slotting on Steyn's UCAs were solely to gain more static negative camber, it would be good for everyone to know it as that seems to be the crux of this entire debate. The presumption that "MOAR KAMBAR" is the salve for what ails us is what's triggering this debate, for which I'm not entirely supportive of being accurate.
I stand by my position the slotting was not solely for "more negative camber" but a combination of that and ride height.