Let's be clear. The original question in the OP didn't have anything to do with numbers of walk-ons starting. It had to do with what position would you be upset that a walk-on was starting. Very different discussion.
So, let's stick with reality and that's anywhere from maybe 2-4 walk-ons starting. I have absolutely zero problem with that if those are the best players at the position and they are playing at a high level...no matter what position that is.
Now, as to the question of "success". Sitting here right now, if we started 4 walk-ons next year and they compete at a level needed for the team to go win 10 games next year, I would be very happy. If we are starting 4 walk-ons 5 years from now and we still haven't won a conference title, I would be disappointed. But, I wouldn't automatically blame the walk-ons That's ludicrous and not fair to them. If the scholarship players can't beat them out, that's on THEM....not the walk-ons. AND....there are 18 other starters (scholarship players) that play a major roll in not winning championships too.