I would find that to be a ridiculous risk for those not actually in the business. The whole idea behind insurance is to spread the risk among lots of people. If a medium-sized business is underwriting their own policy, I would think they would quickly go bankrupt more often than not.
These are far more potent threats to traditional pastoral and agricultural traditions than tax policy. If it was just a bunch of family farms competing against each other (or more likely forming co-ops given history) then it might be a bit more of a fair playing field.
Classifying those with certain genetic mutations as disabled, could be another solution to this problem. Although it should, in theory render them immune from. discrimination, it's a highly imperfect solution that could lead to a very ugly society.
Id rather just keep that information completely private. Companies have been able to operate just fine without the data provided by genetic tests since time immemorial. Employers are not allowed to ask about whether or not you are. married, have kids, your religion, your ethnicity etc. It might not be fair, but it is a trade-off/tax that I would happily pay to ensure that people, through no fault of their own, experience a new class of systemic, institutional discrimination.
OK, but then why would employers even bother to query the genetics of their employees? So they could STILL discriminate on the basis of genetics (regardless of whether it cost them in medical insurance)?
If we care about equal protection of all American citizens -- and I believe that we should -- the solution is not to legally prohibit employers from performing genetic screenings, it's simply to cover healthcare for high-risk individuals, or ideally everyone, at the national level with single-payer care. That way there's no incentive to cheat anti-genetic-discrimination laws, business don't have to worry about getting hit with an unexpected multi-million dollar expense, and the cost of coverage to everyone shows up on the national ledger, where it honestly belongs.