The one thing I ALWAYS advise my clients to avoid is having a judge decide things that they could have decided themselves trough careful drafting of documents.
Under our system of jurisprudence, some things are dealt with under federal law, some are dealt with under state law, and some are dealt with under "common law." ERISA and the tax code pre-empt, but they don't cover everything - so one looks to "state law." WHICH STATE LAW APPLIES is often very complicated and difficult to determine. State law may impact how trusts are governed. ERISA says a trust must be used, but doesn't specify how to establish one (and there is no "federal law of trusts"), and while it may indicate who can't be a trustee (trust me, ERISA has a few prohibitions), it doesn't say WHO can be the trustee. For example, in SOME states, a NON-trust company corporation CANNOT be trustee of it's own employee benefit plan. In others, a NON-trust company corporation CAN be trustee but ONLY of it's own employee benefit plan, but no other trusts. Its State law based (and in that case, there could be a CONFLICT between the state of incorporation (often Delaware) and the state of it's principal place of business (GM is a Delaware corp with it's main office in Michigan - which state governs?)).
Those are the "simple" issues. IF YOU DO NOT SPECIFY WHICH STATE LAW GOVERNS IN NON-PRE-EMPTED AREAS, The judge gets to decide - and that's just plain stupid.... Why not put some predictability in the process and spell it out?