As a practical matter, I doubt that very many (if any) employers ever consider this as a possibility. The argument seems like an unnecessarily strict application of Section 105(h) in any event, particularly when the medical plan at issue is fully insured and not otherwise subject to Section 105(h). Still, I can't point to anything definite to refute it.
Any thoughts?
UPDATE: Actually, never mind, at least insofar as insured plans are involved. I forced some clarification of the argument. Still, for self-funded health plans, I'd bet dollars to donuts that employers don't focus on the potential for discrimination when they subsidize COBRA for a bigwig who's on his/her way out the door.