How would I break it down in an ideal world?
1 kickers
1 punter
4 QBs
15 OL
12 WR
4 TE
5 RBs
8 CBs
8 Ss
14 LBs
16 DL
Not all that different from how I would do it, but I would make a few changes as noted below.
1 kickers
1 punter
*Subtract 1 of these two here and go with a walk-on. I don't really believe in using two schollies on special teams, mainly because the scholarship guys are often outperformed by walk-ons (see Devon Bell, Sean Brauchle, etc.). Besides, I can't remember a single time in the Mullen era where both the kicker and punter were on scholarship. Maybe Devon Bell's freshmen year but that might be it.
4 QBs
*Subtract one here. You are never going to be able to play nearly that many, nor keep that many over the long term as it is the glamour position where everyone wants to see the field yesterday.
12 WR
*About right
4 TE
*About right
5 RBs
*Subtract 1 here. We had 6 this year that had all already redshirted or played, and only 2 saw a meaningful number of carries. 5 is way too many.
8 CBs
8 Ss
*Both about right
14 LBs
16 DL
*Subtract 2 here from these combined groups. If 4-3 is the primary alignment, take out 2 LB. If it is 3-4, take out 2 DL. If it is a hybrid of the two, maybe take out one from each.
If it were me, I'd take all those subtracted and give them to the OL. I understand it can be hard to have that many, but I'd break it down with 9-10 in the primary rotation (as you said), 4-5 deep reserves (guys just coming off their RS year and some less talented upperclassmen, and 4-5 redshirts. Obviously you can give or take here and there with those numbers.
I think even if we can't sustain holding that many OL on the roster, it benefits us to still sign 5 or 6 every single year. Then let the rate of attrition and processing decide whether we fall closer to 15 or closer to 20. It's obvious based on our recruiting limitations (mainly the state in which we reside) that we are never going to consistently sign multiple blue chip OL every year or maybe even any year. So, I say let's take a different approach and increase our sample size at the most difficult position to evaluate in recruiting.