I like that solution. Good idea. The task has a pretty heavy mental fatigue right now (0.4, if my memory serves), so you’d be able to make two per day if you had the batteries. That still seems like a lot, but maybe it isn’t given the need to find batteries. I’m still worried a bit about people finding a first order optimal strategy and just optimizing the fun out of the run.
One other consideration is whether it’s worth adding the special case. I like systems based stuff where behaviors emerge naturally, and adding special checks for whether the person has made a certain number seems to interfere with that. Or I’ll forget and make some change to the intelligence checks and end up with a strange bug.
Perhaps then it’s worth looking back to your earlier point about guaranteed success on any roll. Just thinking out loud: There’s always a 10% chance of success. I don’t really want to change that. If it’s changed so (net bonus after penalties > greater than the check) -> guaranteed success, then once a person’s int bonus exceeds 2 they auto succeed on everything (until they get tired). That seems a little imbalanced. Could also do the D&D thing where it has to be ten-over, which doesn’t have an exact mapping here. I’m going to have to think about it more. If I can’t find anything better then maybe the special case is fine.