Guh-Huzzah!
Totally humorous voice over and YouTube guy.
The Block of wood argument is true. but the same can be said for Pokemon trainer.Frisk being some kind of summoner character makes about as much sense as Shulk doing the same with his companions, or a Fire Emblem character summoning their allies. At best, they'd be cameo's in Frisk's Final Smash like Dunban, Riki, and Fiora are for Shulk.
Plus the entire gimmick of Frisk's character is based around them being able to choose not to fight, and the fact that Frisk is not the most recognizable character in the game, nor the most popular, and the fact that Frisk is about as expressive as a block of wood. They don't fulfill any of the criteria that Sakurai lays down for potential characters. (Nor, arguably, does an Undertale character in general. But we're talking about the merits of the characters in comparison to each other, and in that regard, Frisk is DEFINITELY not the frontrunner)
Your other arguments are pretty solid though. Just makes kinda more sense to me than just one character that isn't even the protagonist or something. Kinda like having Luigi without Mario the way i see it. Pretty solid argument though, like i said