Good points. All true. Except........
So who then are the ten virgins?
Only saints are virgins in scripture. Only saints have the Holy Spirit (oil in their lamps.).
Cannot apply to unbelievers........
Might refer more to the product of the work of the Holy Spirit in their hearts.
The wise virgins remained in fellowship, allowing the Holy Spirit to continue His sanctifying work in us. The foolish virgins did not remain so perseverant.
Remember how our Lord perceived when a woman touched His garment in faith.
When the Lord returns, the HS may have already departed, leaving us with the spirit and sanctification of our souls partially complete, pending the Millennial reign.
Non-church age believers?
Maybe Jewish believers during the Tribulation or from before the church age.
Not exactly sure, but IIRC, believers before the church age did not have the continual indwelling presence of the Holy Spirit. Psalm 51 references that when David asks that God not take His Holy Spirit from him. So that leaves that as a possibility.
I also agree that it cannot be unbelievers.