Condensing suggestions (using DJSERB for each of us). I tried to go with what I understood as 'I like this possible matchup' rather than 'I think this is the best matchup' in order to get as much input consolidated as possible. If you disagree with you having a vote/not having a vote on one of these, let me know.
Death: Poison duo (S), rush mono (S), control mono (DEJB), SoP Wardens (JRDB)
Life: Air domin (SD), speed poison (E), SoP Vamps (JRD)
Time: Speed poison (RSDB), grabbow (S), serpentine (SE), poison dials (JR), sanc stall (BJ)
Fire RT splash (SD), dark domin (S), nymphcord (SDR), SoP Wardens (S), Tempest (E), NT rush (E), sanc stall (J)
Earth: sanc stall (SDE), air stall (SDEB), AM/flooding (JR), grabbow (JRB), speed poison (B)
With this, I'd like to confirm Nymphcord against Fire and SoP Vamps against Life. For the other three, Speed Poison has a majority against Time but I think there's still some loose ends, Death seems to be between the control mono and SoP Wardens, and Earth is still pretty wide open for discussion.
Basman, if you could choose preferences for the other matchups besides Time, it would be a huge help.