I like this idea, but possibly with a slight tweak. How about instead of 5 minutes, people can speed up your upgrades by, say, 4%. That is to say, the total remaining time at the time of assistance would be reduced by 4%. However, only 5 people would be able to help per upgrade. This means that your upgrades could ideally be done in just over 80% of the maximum time. I don't know. Just throwing stuff against the wall and seeing what sticks, haha

