I really like the potential that Boyle showed, it reminded me of Kurt Warner, but I don't think Boyle is ready yet to be the #2 QB (and remember he's going against 3rd stringers at best and maybe not going to make the rosters). But I think Packers.com's Mike Spofford said it best
Kurt Warner played in Mike Martz system which was largely based on deep 7 step drops and deep WR routes, which gives pass rushers more times to get to the QB, which is why Martz's QBs were often injured or struggled or Interception prone. Kurt Warner would stand tall, knowing he was gonna get nailed and throw very good passes. Boyle did that at least twice, where there was fairly clearly a blitz coming up the middle with no blockers left and he stood there and delivered a very good deep pass.
Hundley nor Kizer have shown us that yet. Kizer clearly sees it and runs... IF Hundley sees it... he either runs or throws up a lame duck pass that's going no where.
It's very weird, as far as back-up QBs throwing goes, our current #2 (Hundley) is the most ready to play now, but might have the lowest ceiling of all of the QBs, and our #4 QB (Boyle) might be the least ready now but might have the highest ceiling. Though I think Kizer has great awareness and running ability which help a lot at QB and I think they're still adjusting Kizer's feet or throwing motion or something, because he didn't look as good as he did last year. Or maybe still adjusting to the system.
Edit: Just saw this, which confirms that they're adjusting Kizer's footwork
But it's an interesting question... do you go with most ready now? Or the highest ceiling? Mix of the two?