Another problem with your position is that the wording and grammar of Malachi 1:11 does not require the interpretation you suggest. The conversation between God and the priests is about their failure to present healthy, unblemished sacrifices to God, Who, as verse 14 says in parallel meaning, that God is the great king, and is worthy of only the best offerings. So although the entire sacrificial system does point to the perfection of Christ, the types of that perfection, the animals provided for sacrifice, had to be ceremonially perfect to fulfill their purpose as a type of Christ. Yet these wicked priests were cheating God and defiling the typology by collaborating with the laity to disobey the explicit requirement of the law, that the sacrifice be healthy and unblemished. God required sacrifice that was pure under the law, therefore it was possible for there to be such a sacrifice, even in the type. This means that it is not necessary to conclude that the pure offering spoken of here is Christ in any direct sense.
Furthermore, because, as has been pointed out by others, that incense describes prayer in metaphor, it becomes possible to see the pure offering metaphorically as well. As has been pointed out, our thanksgiving, our devotion to God and His truth and submission to His sovereignty over our life are all accounted as sacrifices well pleasing to and acceptable with God. And as God told Peter, do not call unclean what God has called clean. Note that this is spoken in the context of Gentiles being admitted to God’s salvation and being blessed with the Holy Spirit, and thereby empowered to give the purest offering of praise to God, all without any mention of some bloodless wafer. So these too would qualify as fulfilment of a pure (I.e., ceremonially clean) offering to God.
As to whether Malachi here refers to one offering or many, it is common enough to describe multiple events as a single event occurring in many places, such as Moses being read everywhere. There isn’t one act of Moses being read, but many such acts distributed over many places. We would not be confused by the statement, “in every city you will find a Holiday Inn.” We would not expect there to be only one of a franchise, though we do rightly expect each instance of the franchise to share common characteristics.
And so it is with any pure offering made to God. It is acceptable, because God has made it so through Christ. It is offered in spirit and in truth, because that is what pleases God. And it does not, as with these wicked priests, cheat God, the offering of lame, lipservice worship, which is an insult to His dignity as Sovereign God.
And that’s the decisive point here. God is reprimanding these priests for their failure to obey Him and be faithful representatives of Him to the people of Israel. Verse 11 makes no sense to that conversation if it is twisted into referring to some future act of swapping substances while keeping accidents, more conformant to Aristotle than apostolic teaching. Far more sense is made of this if God here is putting these priests to shame by telling them the offerings of the Gentiles are (or will be) pure and truthful compared to the sham these priests are trying to pull on their Soveriegn King.
That’s one of the key principles of Biblical interpretation, BTW. The conversation has to make sense in its primary context, even if it has a secondary meaning, such as prophecy.
Anyway, lunch break is over.