In a self-funded plan, with a new amendment added to increase the waiting period to 12 months, can the plan offer optional limited benefit plan, paid for by the employer, for the 12 monhts waiting period at the end of which the employee would opt into the regular plan?

I don’t see why not. However, what types of limited benefits would you offer them?

There is no prohibition under ERISA, but be careful of state insurance regulations for a fully insured health plan.

I have been involved with plan design which layered a "mini-Med" policy prior to eligibility for the "regular" plan.

Don't you think it would be hard to get new hires with a one year waiting period for insurance?