I hope that someone can find this idea useful.
Reloadable cassettes being more expensive than they used to be, or I would like them to be, I have tried and failed at opening used film cassettes for reuse without mangling the end cap.
So, I printed some replacement end caps in nylon (Because that is what I have. Likely many other materials would work). They cost less than 5 cents apiece to print, if you have access to a printer. I have been using them fairly carefully and so far they work well. I have only used the caps with Fuji cassettes so far. I don't know how similar other brands are. This website does not permit attaching the .STL file for the part. If there is any interest in the part I could see if I can post the model on some 3d print website.
Bruce
Even if you manage to get the cap off without distorting it, these cassettes have a part of the rim that's cut down and makes it a bit finicky to get the cap back on - not to mention the caps themselves are too tight to put back on (they're not meant to be removed easily). So your solution is a good one. I imagine many people would want that file. One of the problems with bulk loading is the lack of DX cassettes - this is a solution.