There are some RFCs (RFC 5109 and the fecframe draft) which allow (force) the FEC data to be carried in its own m= line (ie Content). We should keep that in mind while thinking about the design...
That said, this also means having a way to group contents.
We should make sure Call is extensible in that direction.
The Content as viewed by the UI would not exactly map onto a singe m= section in this case. This could be solved using a separate interface on the Content a la C.I.MediaMixing (proposed for #28718 but left as "later").
Is this considered as a blocker for Call1?
No, it's not a regression.. And we can add it as a further interface on MD later.