I'm pretty sure it would be more efficient if you state your clear requirements rather than waiting proposals for a very ambiguous request.
Knowing your environment and budget would be a start, what are must have requirements, contract and support form.
Finally, since you're asking for a coding service, posting here might have been better:
https://bitcointalk.org/index.php?board=52.0 thank you sir
I would get opinions about budget costs and actual technical options.
The main idea is simple - users should have opportunity to mix their coins in an easy and fast-time manner.
How it should be done - this question is on the developper side, so I want to talk with experienced people to discuss this project.