Who are these self insured that would/are not included in the "pool".
I suspect this would be government workers and mega huge companies employees. Why not include all health care policies in the pool?
 EVERY entity should be included to increase the pool size. This is really the only way insurance will work. One of the reasons ACA does not work is  that many lobbied for and received exemptions for their particular group. The pool has been limited in size due to those with political connections. Check ACA for exemptions. You will be astounded at the groups that are not required to participate.
I support ACA by the way but the entire process was queered when the law was written by the congress and industry to allow special exemptions.