Speaking for cloudflare - some of the online exchangers from bestchange use it successfully and there are no mitm attacks or anything else
The difference between them and your service is that they are exchangers (some of them are AML complaint) and yours is a mixing service. You do realize that when you start mixing coins, Governments and law enforcement agencies could start surveilling your service?
How do you guarantee that your customers are safe from surveillance when your service is using Cloudflare?
Blender.io was using cloudflare for years. Plenty of Russian darknet forums use or used cloudflare. If you have some other alternative but cloudflare let me know