Chapter 1037 has already shit on your theory right there. Luffy is fast enough combining Gear 2 and Gear 3 creating the Rock series.
Not just that but chapter 1009 also shits on your thoery as well. Hybrid Kaido was dodging base Luffy punches with internal destrucrtion haki.
King never stood...
Obviosly Luffy would ebe tmaching Kaido blow for blow as he is using Future Sight, Advanced Armament Haki and Advanced Conquerors Haki together with Gear 2 + Gear 3(at the same time).
The Gear 2 + gear 3 combo is overpowered. The last time he used it was againt Moriah.
That was straight pis against Luffy. We know this becuase he was not using FS or Advanced Armament haki against ulti.
This is shown when we see base luffy using advamced coa onternal destruction haki and future sight being dodged by hybrid kaido in chapter 1009 before he even unlocked CoC caoting.