Heavy gates that are used D3, D7, D11, and D12
Of course in real life they can but, when this happens (not a normal procedure), the gate use the alternate stopping position, which is indicated with a yellow dashed line, but this requires that NO planes must use one or both nearby parkings so, when the alternate position is in use, Ground Control must coordinate and ensure nobody would use the nearby parking.
Take D3 for example, in order to park an heavy airplane using the *alternate* (dashed) position, which would result in the plane better fitting the parking, it's clear that D5 must be empty, since the dashed line runs between the normal D3 and D5 positions.
This is what happens in real life. The sim doesn't support alternate parking positions for the same parking and if we just made two different parkings, to the sim they would just look as overlapping parkings, causing troubles to both AI and jetways. Default ATC, of course, wouldn't be able to deal with this too.
So, the only heavy parking we could add, were those that can always used under any conditions, using their standard positions.