Okay, so:
Every track layout in the game that is playable in multiplayer* has an area where the game starts all the cars in Qualifying when in lobby races or GTWS. This area has to be able to hold the maximum number of cars that track layout allows**. This area is a pitlane for every track layout in the game except for Catalunya Rallycross, where it is the starting area; but it must not be on the circuit itself.
This is not a problem for fictional circuits, as PD can put pitlanes wherever they want (Maggiore has 3, for instance). But it means that layouts of real world tracks that do not have such an area, like
Red Bull Ring Club or
Nürburgring Müllenbach, or ones where the facilities are not up to par for the number of cars they'd need to hold, like Suzuka West, should not be expected to ever come to the game.
In the case of Yas Marina, it has two pitlanes that are viable, so the North and Corkscrew layouts that use the main pits and the South layout that uses the secondary one after the chicane are all possible additions (though Corkscrew seems a bit of a pointless one to me, it cuts out like one turn).
*Nürburgring Nordschleife Tourist is not playable in any mode that starts you in the pits, so I have no idea what the behaviour is there.
**16 for all Lake Louise layouts and Catalunya Rallycross; 20 for all other track layouts.
Why? HP & PS ratings are both derivative values, one imperial, the other metric, and both only relevant to give the marketing wonks something to play with.
