I agree but it's hard to include Clapsaddle and Blalock when they were out of the sport for over 2 years.
I don't think Clapsaddle was ever going to play again regardless after tearing his ACL first game of JV in '16. Not with him being a potential D1 baseball prospect, just too much risk. But even if he hadn't transferred and had he decided play I don't think he would've started on this year's team as a 10th grader, at least not with Vining playing.
As for your son, he had a lot of natural talent but he missed out on a lot of developmental time and seemed to lose some of his athleticism with the added weight after freshman year. How he would've factored in comes down to what kind of shape he was in and what kind of mindset he had. If those things were in order then Roberts, McTaggart, Cruse and him could've been an awesome quartet of linebackers.
The other two players you mentioned are less hypothetical, had Vining's dad not pulled him and had Cruse been academically eligible, they would've helped on offense certainly but where they really would've impacted the team was on defense. Those two would've made what turned out to be a really good defense just flat out nasty.