Account vetting, deposits, or actual identity verification would be a good start. It'll be hard but if your company is planning on making money off other people

Account vetting, deposits, or actual identity verification would be a good start. It'll be hard but if your company is planning on making money off other people lending their expensive equipment out you should really make sure you're protecting those people because they're the heart of your business. Reimburse the lender then go recover that from the thief, if you're doing validation and security well enough it should be easy to find them and rare enough the extra costs aren't back breaking.