This is a typical ethical conundrum. What to do; what to do? Each of us has to answer to our own ethics and our own guiding rules and hopefully they will not conflict. What would I do? Let me think....
1) Resign. Immediately, with a letter and an explanation that I believe they have both disqualified their plan (the 415 issue) which means their rollover IRA is "no good" and subject to the 6% cumulative compounded excise tax which will eventually take 100% of the rollover as an excise tax when the IRS challenges it, and I would also explain that they have actually stolen money from other participants and besides possible criminal penalties, IRS penalties and DOL penalties, their bonding company is also going to go after them since the bonding company will have to make the other participants whole to the extent of the theft.
2) No way we are going to prepare a 5500 at all; see 1 above. We no longer work for this crook.
3) Now the hard one: what do I do about reporting this to someone? I'm pretty sure I don't have a legal obligation under the society ethics rules. Now, what about my moral responsibility? If a participant calls, I'm going to tell them to contact the DOL since I no longer work for the client. Since I have never actually had to deal with this kind of an issue, I'm not sure what I would do. My heart tells me that the crook deserves to be taken to task, which would mean the DOL has to be notified. Is there a John Doe notification to DOL like IRS has John Doe ruling requests? I'm sure a private phone call to the local DOL office will get action. Would I do that? Hmmmmmmm.......