Sounds logical to me. Legal action takes way too much time. There’s nothing wrong with including backdoors as long as they can be removed once you’re paid in full.

However, you’re better off investing in your brand/status in the future. This will attract more clients that are willing to trust & pay 100% upfront.

Bad faith clients are a hassle to deal with as a whole. You want to clients who require you to compromise your terms of service.