Adding a 401k Plan

A potential client has an existing defined benefit plan and would like to add a 401(k) Plan. His current TPA does not want anything to do with adding a 401(k) plan. Are there any pitfalls to adding a 401k plan to an existing defined benefit plan?

Top heavy coordination.

Combined discrimination testing if tested together.

Combined deduction limits if DB is not PBGC plan.

The usually compliance testing issues.

It adds complexity for sure, but in my opinion, as long as you are competent and capable that is no reason to "not want anything to do with adding a 401(k) plan".  

Of course there are also times when clients (or the client's CPA/adviser) want to add a plan or plan feature that just does not make sense...