I'm working with an employer who we have determined is a local governmental employer for ERISA and tax purposes.

Their head is maxed out in their defined contribution plan. On their face, the Code sections exempting local governmental plans from minimum participation and discrimination provisions, etc., would appear to allow them to put in a 401(a) qualified DB plan benefitting solely the top person (we've also discussed drafting it to benefit a few other of the key executives). However, this seems a way to permit additional executive deferred comp in a way contrary to the policy of 457(f), and I have not found any PLRs addressing this.

So far, I've found nothing in the state statutes that would prohibit this either.

Has anyone done something like this in practice? I'd appreciate any suggestions or thoughts.

Why not use a nonqualified DB plan for the exec? This would avoid all of the qualified plan requirements.

A tax-effective non-qualified db plan with vesting is impossible, due to 457(f).

Exactly. Furthering the problem is that the executive contemplates wanting to do some paid consulting after leaving the current employer. He would like to be able to keep from receiving his deferred income until a date well after his termination with the employer. Consequently, simply keeping the executive unvested until he terminates doesn't help him much.

You could use a 415(m) excess arrangement. It doesn't work for anything except a 415 excess but it works for defined contribution as well as defined benefit. Also, 409A doesn't apply to it.