This sounds like a great idea and I think the case sizes Chuck mentioned are pretty indicative of the ones a club would need.
Another option to consider would be to have about 5 each of some of the popular DMS motors on hand and then sell them to cert fliers at cost to avoid any issues with being a "dealer". Cases and closures will break and require maintenance. One CATO will be a significant cost to the club, if the case/closure gets ruined. DMS motors remove the maintenance and damage issue and are essentially a net zero (outside of initial outlay) cost to the club. This option would also help out new fliers by removing the obstacle of obtaining high power loads prior to a launch. You have to put some controls in place to make sure the motors only get used for cert flights, but that should be easy.
I think the following motors would cover most L1 and L2 attempts. Anything outside of these would be something the flier would have to worry about:
29mm H115
38mm H100
38mm H219
38mm J270
54mm J250
Looking at the costs, if you went with the motor cases, the cases you have listed above would cost about $1500 upfront (2 each, with closures), but would incur the costs of ongoing maintenance and replacement.
The initial outlay for the DMS motors would be about $1900, but would be a one time cost as everything in the future would be covered by users buying the motors onsite. The cost to the flier should include the shipping cost prorated into each motor so the club wouldn't pay anything out of pocket. I have a feeling that, over time, you would see some trends in which motors get used more and then could adjust your stock accordingly.
This would also alleviate all the issues with novice fliers having to assemble motors for a cert flight.
I am sure there a lot of reasons this wouldn't be a great idea, but it seems like a possible alternative to cases. That amount of motors is quite small - they would all easily fit in one of the Aerotech shipping boxes, so storage between launches could easily be on someone's garage shelf.
Does Aerotech have any programs in place to support clubs with this kind of thing? It would seem to be good business for them to support this kind of initiative. If every club did this, it would seem like a guarantee of hundreds (thousands?) of DMS sales a year in predictable motor sizes that would streamline the manufacturing costs.