Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
I'd equip them with P-40Es. It's faster then the A6M2 and Midway had radar ground control. So with proper training (however unlikely) the Marines should have the upper hand.
Bear in mind that VMF-221 were still using outdated division tactics and, for the most part, were inexperienced pilots many of whom were straight out of training. Given these facts, I don't think substituting the F2A-3s for a different aircraft would have made much difference.
In my very 1st post, I said it would be fine to sustitute USAAF aircraft and crews, so you are not limited to re-equiping the inexperienced Marine squadron on the island.Since it was a Marine squadron, the only option would have been Wildcats and they weren't available in sufficient numbers (or there would have been more of them at Midway in the first place). However, per my previous post, I very much doubt if changing equipment would have, to quote you, "done a better job".
But nothing really changed that much between the Marine fighters at Midway and early Guadalcanal. The units at Guadalcanal, especially the early ones, weren't that much better prepared. The famous fighter leader at G'canal, Marion Carl, was present in the Midway fight (flying F4F-3 and credited with a Zero) but otherwise most Marine units at G'canal saw their first combat there. And Marine F4F tactics at G'canal were improvised as they went, and in many cases don't fit the standard thumbnail sketch of tactics evolution v the Zero (for example later in the campaign the Marines sometimes sought to dogfight Zeroes, while the IJN units sought to 'hit and run'). The tactical situations at G'canal were often different, OTOH that of VMF-221 at Midway was not that terribly unfavorable, outnumbered, but they were above the Japanese force when the combat began.Bear in mind that VMF-221 were still using outdated division tactics and, for the most part, were inexperienced pilots many of whom were straight out of training. Given these facts, I don't think substituting the F2A-3s for a different aircraft would have made much difference.