Individual CB/DB plan for partnership members with no employees

This is for a medical group partnership with no employees and all HCE's, common in emergency medicine. Each member is a separate entity but the group is an affiliated service group.  Are individual cash balance plans allowed?  I believe some members may have them already.

The ASG is treated as a single employer for purposes of 401(a)(26). Since plans may not be aggregated for 401(a)(26), any plan put into place would have to cover at least 40% of the ASG members (or if there are only 2 members, both members).

That's what I thought. Would it be possible to get a group plan for 40+% of the members and then run the DB through that?

Sure. They could have the partnership adopt a plan and then have the member orgs as additional adopting employers.