I think this is as simple as them letting the league know that SJ39 is available for the right price. This is gonna be his last year in STL, and they've got nothing to lose by floating his name out there and seeing if someone is desperate enough come playoffs time to offer up something crazy like a 2nd or 3rd rounder for him (never gonna happen, just sayin).
The other option here that might work on a much lower scale is, IMO, Bradley Fletcher. He's a guy who was expected to be a top 2 CB for the Rams in the old regime, but has quickly been downgraded due to the arrivals of Cortland Finnegan and - especially - Janoris Jenkins. Fletcher has been riddled by injury in his first 3 years in the NFL, but he's played pretty well this year, is in the final year of his contract, and could really help out a team in need of some depth at Corner as they approach the postseason. I doubt the Rams would get much of anything for him, but if someone were willing to offer, say, a 5th rounder for him, I think the Rams would ship him out. Fletcher, as opposed to the Jackson, is a guy I think the Rams would like to re-sign and bring back at the right price if he remains with the team. But if they could get a desperate team to offer up a 4th/5th rounder for him, I think they'd consider it.
Other guys who could be considered in a deal would be, my best guess....Harvey Dahl (signed to a pretty big contract by the old regime, would be tough to move) or Quentin Mikell. But again, IMO this is all about seeing if anyone would pull the trigger on a SJ39 deal.
12 team standard
RB: Forte/DMC*/West*/Langford*/Rawls/Buck Allen
WR: A Robinson*/Amendola*/Watkins*/Hilton
(RIP Charles :F )
(RIP Foster :F)
(RIP Edelman :F)
(Get well soon Forte, West)