I would tend to lean pretty heavily toward Shields and Starks both not returning which would free up another $12M.
It was a mistake to retain Peppers this season as that additional $8M in cap carryover would have been much more valuable than his contributions this year.
Peppers being a free agent does not enter into the the numbers presented above, other than he'll need to be replaced.
Whether he was worth the $8 mil in cap is water under the bridge and 20/20 hindsight.
From my perspective, going back to before the 2015 season, copiously documented at that time and since, 2015- 2016 was the window of opportunity. That makes this season an especially acute disappointment.
As for Shields and Starks with their $12 mil savings:
Without those guys, regardless of what you think of them as players at this point, the Packers then need to come up with a shutdown corner since Randall is not that guy. Without Starks, 2 RBs are needed assuming Montgomery assumes the role of 3rd. down back, which he should. The numbers above include nothing for Lacy, assuming he departs in free agency. So it's not j2 RBs needed; one needs to be a quality lead back. Michael will prove to be a Montogomery redundancy, and a lesser one at that.
Assuming Shields cannot return, I would make the following moves:
1. Move Dix to nickel DB; Hyde will be gone in FA and he's looked pretty bad this season anyway
2. Move Randall to FS
3. use Shields savings to go into FA for a decent man coverage corner
4. draft high for a starting corner if Rollins doesn't shape up in man coverage over the remaining games
This would assume a change in regime that has the breathing room to use 2017 as a semi-rebuilding year.
With or without Shields and/or Starks, there is a lot of work to do given the available cap and the 2017 draft.
If, by chance, the Packers go in a new direction at the GM level and a 4-3 D specialist were to be brought in, Matthews would be out of a job yielding an additional $11.1 mil in cap savings to enhance the process. I'm not sure he hasn't exhausted his value at that cap number even in the 3-4, though somehow Perry plays better when he's out there even if Matthews is single teamed.
In a 4-3 D, the backfield changes or enhancements in the current 3-4 apply then as well. The D-Line would look like Perry-Guion-Daniels-Clark, assuming Clark can use that useful quickness he was drafted for to beat some OTs in the pass rush. Maybe Daniels/Clark would need to be switched, but Daniels is best as a run stuffer and his lack of length could prove to be a liability at DE. I didn't mention Pennel in the above numbers, but he'd be worth bringing back on a modest deal for DT depth. Subtract that deal from the cap number.
I think there's plenty to work with here in a 4-3, but you may need to get a bookend pass rusher to pair with Perry in a rotational role. Maybe Fackrell if he puts on some good weight.
Ryan at MLB, Martinez at OLB, Thomas at OLB (though I believe Thomas' coverage skills are overrated and would likely need replacement). The 4-3 OLB needs to defend the run in space, working off those second level blocks, cover backs and TEs, and preferably add some blitz capability.