I wasn't aware the ACA made pooling illegal. Awhile back I tried to form a group with small tech companies in my town to do this, but the insurance companies all wanted a larger anchor company. None of the bigger tech companies in town wanted to participate b/c they saw their benefits as a competitive advantage. This was post ACA, and I don't remember anyone mentioning legality.

Small companies get crushed by insurance. Giving employees extra money in their check and telling them to use it on the ACA is probably most effective for all parties at the moment.