Ah! That's a good point... The latest version of rental piranhas come with a quick strip pin that has a locking mechanism, so that a renter can't remove the pin on the field.
I have a maintenance contract with one of the local fields, and repair all the broken guns... The have Piranhas, Prolites, and 98s. Being industrial minded, I keep a maintenance log with the serial and problem with every gun that comes in.
Last batch, I had 23 piranhas and 7 98s. The prolites aren't worth mentioning because of how long they've been in service (a long time, but every other one that breaks down is done for good.)
Of the piranhas, 15 just need cleaned and/or the ring replaced on the hammer. 6 had sear issues and either needed a new hammer or a new sear. And two were unfixable because the trigger sear pin had fallen out of the trigger and we don't stock those spares. To troubleshoot and repair a piranha takes about 10 minutes.
I DO feel like hardened components would eliminate almost all of the sear issues. And because you would probably clean them for storage after each use, the 15 "needs cleaned and oiled" guns wouldn't present an issue.
Meanwhile, the 98s all either had a powertube crack or a sear issue. So every one that goes down needs parts ($). Troubleshooting and repairing can take up to 45 minutes each unit. The clamshell design just makes it ridiculously hard to work on. If you have multiple problems with one gun, you end up taking apart the gun multiple times.
There is a modification that some people have done, involving cutting one shell of a 98 on a bandsaw, so that you can access components a lot easier, with fewer screws.
From a feasibility standpoint, either type of gun will work... Especially considering that you'd put less than 100 hours playing/year for each gun you get for this purpose. Which gun type you prefer to service should probably be the deciding factor.
Something else to consider is that if you're gaining access for as long as you're lending guns... Then the guns are yours. And if you're picking them up for 20 each or so, then you can certainly liquidate them at 20 each when you no longer want to play there. And the bulk of the time, you won't need to keep 14 guns running. It will usually be just one or two lent out.