Yes I agree with Bob the Swimmer. What does any investment committee do when EEs ask for a certain type of fund to be included in the fund lineup? Whether it's emerging markets or contra funds or real estate, etc. the committee should consider the request along with its advisors and either adopt a change or disregard/table the request, but document the prudent decision-making in meeting minutes. Then someone can call the EE and explain why...e.g., "already too many funds in the plan or we have it on our future agenda, or can't find a good fund, but will keep looking and thinking about it."
As far as the link and someone trying to opt-out for religious or other reasons, I agree with the train of thought in the link that if you can't opt them out under a general clause (whether by amendment or if an opt-out exists in the plan already) or if you can't or don't want to find a suitable special fund to add, or other suitable compromise under the terms of the plan, you must follow the plan design and give the EE an account. Later if they refuse the distribution of their vested account you escheat it to the state but you can look an auditor in the eye that you have maintained the plan according to its terms and the regs. I think that's your overriding requirement as an administrator until the DOL says otherwise. The DOL has some skin in this issue to advise on conflicting federal laws. If one of my EEs came to me I'd call the DOL and if possible submit some formal question to them and put the burden on them.