Threads... I've shortened bolts before and it is possible, but there are a couple problems with it. First of all, if you bugger the threads up, you can't get a nut started. In this case you have a cast coin door to thread into. If you crossthread that, you are screwed...or not so much I guess. Second, and less of an issue here, you are cutting through the coating. Zinc coating helps prevent rusting in a low corrosive environment. If the end of the bolt has it's coating removed, it's technically possible that you will see rust form there quicker than an uncut bolt. If you rust the bolt into the coin door, you will not be taking it off without a grinder.
Also, I said that the washer might get in the way if a coin box is used. If not, then no need to grind.
Beyond that, that clip is designed to thread onto the bolt. It requires being placed in the right position on the bolt for it to hold the door securely. That may be a challenge in the first place, but beyond that, the clip is relatively thin and probably won't make the coin door truly secure anyway.
You can make bailing wire work too!