I think it's an interesting original post. What kind of athlete works best as QB in our system (AB, BB, WR)? Of course, you'd want it all, but we're not going to get it unless Calvin Johnson has a son who ends up playing QB and wants to make his grandparents proud. Even then, nobody has it all. You're never gonna the lovechild of Bo Jackson, Barry Sanders, and Joe Montana who can do everything that all 3 of them could do. If you get 2 out of those 3, you've got a new legend who will win a Heisman and a Superbowl by his 24th B-day.
As others have said, you can be successful in our system without being a world-beater in any area if you're pretty good at a few things. There are 2 things that aren't compromisable (not a word?): good feet and a good arm. Size is an added bonus. JT was obviously successful. JfN was obviously successful. Tevin was decently successful (and had no outstanding traits save a grasp on the system and just enough athleticism). Heck, Tim Byerly might have been as good or better than any of them if he had one more year - dude could throw very well and was as strong as JfN running just not as shifty and cool as a cucumber (like JT). I would like to have seen what a season led by him would've looked like. Those strong guys can move the darn chains, which is something we've missed in our worse years with smallish guys. Taquon looks like he could be the most special/electric runner we've seen run this offense. I love him at QB. I think he can improve with mental efficiency and obviously lacks a little in passing. I think he can be ultra effective with a good supporting cast.
But, it would (will?) be interesting to see other types of athletes at QB for us. Would've been very exciting to get that Barrett guy - looked like a BB who could throw well. Looks like we've got another JT/Taquon type in Graham. And, it will be fun to see what a higher level thrower like Lucas can do. But, here's a third uncompromisable trait - the DESIRE to run our offense (and the toughness).