Honestly the keeping him while threatening suspension for conduct detrimental or outright benching if it comes to it is more and more appearing to me the most logical route to take if they seriously think they're still legitimate contenders (I don't believe it but they probably do).
As I understand it, because of the restructuring they gain practically nothing in cap space from trading him next season (unsure of what the ramifications are past that), so whether he's off the team or not the value gained is negligible to that end.
Due to his antics his trade value is likely declining by the day, so hoping to get anything of draft value back in return to bolster your competitive chances going forward is progressively dwindling (the chances they hit on another 6th round eventual all-pro isn't all that likely).
So the main benefit to the team in getting rid of him, whether it be by trade or release, is simply not having to deal with the headache of him still being on the team and damaging the locker room, which does have value however quantifiable.
The way I look at it though, is if as said they seriously consider themselves still contenders, then there is also value in him still being on this team even if benched or suspended rather than on another team, making a potential playoff opponent better.
It's the same reason there was still value in not just rescinding the tag on Bell once it was fairly clear he wouldn't be back, because as long as he was sitting out the year in protest of the franchise tag, he wasn't playing for another team you may eventually have to face (of course when you miss the playoffs that makes the whole point moot but still).
I highly doubt they'll actually go that route of course, because I don't know if it's ever been done before nor if the players association wouldn't have a legitimate grievance to file (they probably would), but logically the more this goes on the more it kind of makes sense in a twisted way. If they're damned either way, him not playing for any team is better than him simply not playing for just this one, as long as you can keep the locker room mentally intact, which is a different story all together with this coach.