From your post, the objective of such differentiation or assigning such title is not known. An employee is different from a retainer. Again a commission agent (there cannot be a Commission Employee) is different. Similarly, a Service Provider is is not an employee and the role that he plays is entirely different. If the objective is to deny any rights conferred to an employee, then you are mistaken. Whatever be the agreement, the function or the work that he does defines whether he is an employee or not. As such, if you engage a retainer on a retainership agreement and ask him to come at 9 am from Monday to Saturday and remain for 8 hours and allows him a casual leave per month or deduct salary for the days not attended, then he is an employee only. You cannot engage an unskilled worker as Retainer!
A Commission (agent) is one who does some activity, say selling the products of the company, in return for a remuneration called commission. The commission should be variable from the first unit of sale and without any limit. Like Retainer, he is not guided by the code of conduct or HR Policies of the company.
Service provider, say someone who carries out an operation on behalf of the employer, again will be providing the service irrespective of any time, intervals, presence in the office. The Service provider submits his invoice for the services rendered and claims the amount from the company.
Very short, you cannot run a business with out any permanent employee in it. If your nature of business is permanent, you should have permanent workers.