CuseFan has the best suggestion. Restructuring is sometimes also known as component testing. both testing groups would have to meet minimum gateway. Generally the youngest HCE + older NHCE are put in a group and tested on a contribution allocation basis, the older HCE and the younger NHCE are tested on future basis.
For next year - I would not suggest adding in allocation conditions - if you do , it handcuffs who can receive an discretionary employer contribution. Your plan document might waive allocation conditions for purposes of meeting gateway, but what if a younger NHCE left partway way through the year, and it would be advantageous to testing to give that person a larger contribution? you would not be able to if the plan has a last day employment condition. That person would be limited to the Safe harbor, and perhaps gateway.
I do suggest that safe harbor nonelective go to NHCE ONLY in plans that are cross-tested. If it works out to give the HCE 3% and not skew testing, that can always be accomplished with a discretionary contribution.
Alternatively - for some future year - if the plan is small, owner comp is high, and general participation is low - sometimes it works out better for the plan to use safe harbor match. The owners defer the maximum, if their comp is high they can receive a large match, and then make up the difference in discretionary employer. Depending on the specifics, it might get the owners to the maximum overall limit with less minimum to the NHCE to pass testing. May not work as well if the plan is top heavy. But something to consider sometimes.