I was trying to think about this because I look at Stealth specifically as a "if a tree falls in the woods" problem. If you hide when nobody's looking for you, does it matter if you're hidden? To me, no, but Mouse isn't asking specifically about Stealth.
What about demolitions work, then? I could see a base difficulty needed to properly set and arm explosives, but your roll could still be contested if someone wanted to disarm your bomb.
Driving in a chase: You have to make at least, say, a Good roll to make the jump over the ravine, but your roll's contested by the guys trying to catch up to you as well.
So yeah, there are other situations where TheMouse's suggestions work. And I think his suggestions seem okay BTW. Just flip the penalties into bonuses, like in percentile systems where a +20% is a bonus if applied to the skill, but a penalty if applied to the roll.
I pretty much still look at it as a 'tree falls in the forest" type issue. Perhaps I just haven't really encountered the issue Mouse is concerned about, or perhaps I have a workaround which I just automatically have been doing.
With regards to both examples of a setting and then disarming a bomb, and a car chase involving jumping a ravine... From my perspective, neither of those are really opposed roles.
Setting a demolitions charge would be a straight difficulty to set (properly), as well as a straight difficulty to successfully disarm said charges as well. The number of shifts of success the person setting the charges achieves would dictate how effective the charge is once it goes off, assuming that even happens (either by failing to successfully set the charges or being disarmed). It is also quite possible that a very poor roll while setting the charges could cause them to go off prematurely, either trapping the person setting the charges, or perhaps just turning them into chum.
The reason (from my perspective at least) that the difficulty to disarm wouldn't increase is because if someone is using a normal type charge, there are only so many components involved and only so many ways they can be arranged. A basic example would be something like dynamite, a blasting cap, battery/electrical source, and a trigger to complete the circuit. Unless the person setting the charge goes out of their way to make it more complicated, adding redundant items like multiple triggers, auxiliary electrical sources, etc to it more difficult to disarm, then it should just be a straight difficulty to successfully disconnect some of the items to disarm the charge. If the person setting the charge wishes to make it more difficult, they of course could choose to do so,
prior to attempting the skill roll for Demolitions, which would have an increased difficulty because of the extra work the person is attempting with the device. My reasoning behind this increase in the difficulty to set the charge initially is because by adding extra items to the charge to make it more difficult to stop/disarm, there is a greater chance for something to be set incorrectly and either not have the charge go off, or have it go off at a time when the person setting it doesn't want it to (like when it's in their hands...)
With the car chase and having to jump a ravine, there are two parts to that. If both the chaser and chasee are traveling a path which forces them to jump a ravine, the ravine is an obstacle which both parties will encounter. Presumably the chasee has the head start, and would encounter the ravine obstacle first. If they pass their Drive skill test, then the chasee can proceed past the ravine, if they fail, then they would most likely have some sort of car wreck and the appropriate results from that. The chaser, once they come into contact with the ravine obstacle, would also have to pass the appropriate Drive test, whether they have to jump it to continue on, or stop short, whatever is required. Now if the chasee fails the Drive test and the chaser passes, then yes the chaser should be able to 'catch' the chasee since they would most likely be crashed in the ravine. However, if the chasee passes the Drive test but the chaser fails, then the chasee should be able to escape easily since the chaser is the one who crashed in the ravine. It's also quite possible that both parties ended up crashing in the ravine, which would mean that the chaser did catch up to the chasee, but either group is likely in any condition to do anything about it.
-Cheers