Schenn for OEL is probably a good basis for a trade, but i doubt STL moves Schenn having JUST extended him for 8-years at a reasonable cap hit ($6.5M/yr). That wouldn't sit well with free-agents, but in a fantasy hockey scenario, you'd have yourself a deal. In the real world, I just don't see it happening. Blues would need to bank some cap space in such a trade as well, so you'd likely need to take back Steen, Bozak or Allen.
Tampa may have the forward depth to beef up their blueline. Gourde (for salary) & Cirelli for OEL? Cap would be a concern there too.
Philly may be willing to part with Nolan Patrick with Frost and Rubtsov close, and Cooter, Hayes, Konecny & Laughton in place. Would probably need to send back Gostisbehere in the deal for $$$.