Problem here is with the notion of "interior" intention. Interior/internal only speaks to the fact that it's internal, an act of the mind and will, vs. just physical activity.
What's at issue is not whether it must be interior or internal, but what the OBJECT of that intention must be.
Again, the object of said "internal" intention must be simply to DO that which the Church DOES. One need not intend the same thing the Church intends by doing that action. So what's under discussion is the OBJECT of said internal intention. If one must intend what the Church intends, then pagans could never validly baptize. But if one merely intends to DO that which the Church DOES, then anyone can validly baptized.
And notice the language of Trent; one must intend to DO that which the Church DOES. No mention of someone having to intend what the Church intends.
Let me give you an example of where the interior intention is lacking. Let's say you have a priest who's just practicing offering Mass (for whatever reason). Perhaps it's because he's been just conditionally ordained from the Novus Ordo but doesn't yet know how to offer the Tridentine Mass. He does everything including saying the words of consecration. But his intention is just to "practice". In that case there's no intention to perform the action that the Church performs. This would not be valid. So the mere external action of saying the words does not suffice to validly confect the Sacrament.
But, on the contrary, if you have a rogue priest (say, some Communist infiltrator) who goes up there and says Mass for the parish. In his mind, he's saying "I do not intend to consecrate." This matters not. By going there and publicly offering the Mass, he intends to DO what the Church does, to PERFORM the actions that the Church performs in order to validly offer the Mass. That act of the intellect & will (internal actions) suffices to make the Mass valid, despite him intending NOT to do that which the Church INTENDS by the Mass.
That's why, regardless of what rogue infiltrators might be in the Church, God will safeguard the validity of the Sacraments for the faithful. God doesn't withhold the Sacraments from the faithful due to such rogue elements.