The format is a bit wrong, $Wm and $Ws both call FIDs, none of those call MPIDs, those come automatically with the portrait since the FSID need to have an MPID assigned to them, so that they can work in supports.
Here's an example of me using that line and it working;
(the sweat drop seems to be incorrectly aligned to the _st portraits, it seems that needs to be fixed in the FSID_ST_ block);
MID_DIE_新ティアモ: $t1$Wmティアモ|3$w0|$Wsティアモ|$Wa$E苦,汗|I can't let it end like this... I still have a lot\nto give. I'm falling back...$k
Where 新ティアモ is the PID (new tiamo) and ティアモ (tiamo) is the FID.