Difference between MESECAM and French SECAM is how it's stored on tape, the composite/s-video output is SECAM in either case so that is what the device needs to support. (There will be differences between SECAM variants over antenna cables but that's generally not something one would use for capture purposes anyhow.)
My Video gear overview/test/repair/stuff yt channel http://youtu.be/cEyfegqQ9TU
Did the OP already try to capture from the component video output ? how would an HDMI passthrough device handle SECAM/MESECAM ? only very few vcr's recorded the pure SECAM signal to tape, isn't MESECAM converted during playback to PAL, and gives black&white on output when not converted by vcr ? PAL is always on output vcr ?