How large could Arthropods get if they had better vascular & respiratory systems?

I've looked into Arthropod evolution quite a bit, & I know that insects' main size limitation is their reliance on direct diffusion of oxygen through tracheal tubes, & Vertebrates are able to get so large because of our gills/lungs, & our vascular system that can transport oxygen without insect trachea.

But certain species of crustacians (including the largest terrestrial arthropod, the Coconut Crab) have evolved Branchiostegal Lungs, which allow them to get larger than other terrestrial arthropods, like Spiders & Insects. And while I haven't been able to figure out exactly how these things work, it got me thinking...

What if arthropods evolved an actively pumping vascular system similar to Vertebrates, & evolved a mode of breathing that allowed them to gain as much oxygen as vertebrates? Could arthropods even reasonably evolve this kibd of vascular system? And if they could, how large could terrestrial arthropods get, assuming there's another limiting factor?

(Hopefully I phrased myself well, & thank you for reading through all that 😅)