I think the duty wouldn't work as a split shift. I did indeed mention the 11 hour rest period but I think downroute the rest period can be reduced to 10 hours. I'm a bit rusty of the FDP front.
Even so, it's not that long a nightstop. Typically, nightstoppers tend to land between 9 and 1030 anyway so there isn't really anything dramatically different. The aircraft lands around 2020 (thats local btw) and it's needed the next morning to operate the flight back to MAN. Therefore, theres nothing else for the aircraft to do other than sit on the ground in MAD and the crew need their rest period. It all sounds perfectly plausible should it go ahead.
Now for a split duty scenario to work it would likely see the service depart MAN around 1030PM arriving MAD 0150am and then the crew would HOTAC for 4 or 5 hours before departing back to MAN.