FWIW, while I'll not argue or speak against any decision as made by the mods, the sort of "mirror" version of Osgood seems the best option since timeline-wise dividing them up is actually REALLY complicated for plot and an unwise idea.
In the case of Osgood vs. Osgood, this is not like a set of twins, but absolutely requires a single player, rather like Akito and Agito. Same brain, same experiences, except differing in the case of Ak/gito, same personality and voice. It's like a superhero disguise except in the case of Osgood, the disguise is the opposite. Given the rule about Ak/gito requiring the same body in order to keep it easier for other players to interact with, IRONICALLY I would suggest that it's easier to interact with Osgood having a double.
Osgood is an exceptional case to the zygons, BECAUSE of Osgood's extreme personality. She's so overpowering that she overtakes the zygon's individual personality and it becomes preoccupied/"possessed" by what Osgood wants. There are some other cases where this could happen, (such as with the clones including that of Amy, who were capable of being so convinced they were those they duplicated they were prejudiced against other clones) but Osgood is the only case for the zygons, which makes her extra difficult to play without her real duplicate purposely BECAUSE of how others treat her. She doesn't actually interact with herself, she only notices the ABSENCE of her other half. -> Something that would make for a more interesting character development event if Osgood (one) was ever killed, because even then the remaining Osgood would go into hiding (as aforementioned by her player) and fret about a zygon/human takeover until rescued/etc.
I know that's REALLY confusing sounding, and it's all VERY timey wimey, but basically, I'd rather Osgood could have her duo-part as still part of the one same person and player. It's sort of opposite how the Doctors are separate personalities that do in fact interact with each other, Osgood has no need of it because she is the same, with the same goals, same mind, same process of thoughts, and no change of mind. There's no need to talk to each other or interact, and indeed, they could not be played separately because every thought is the same and unlike twins, they aren't basically overcome by one identity. With the Doctor, it's different because he treats himself very differently and unlike Osgood, fights with himself, rather than having the same goals in mind, and indeed, each incarnation has a different thought process as well.
In my opinion, it's similar to how the Moment/Big Bad Wolf takes on Rose's personality and face, by borrowing the moment she rescues the Doctor, and then has the same goal in mind. I would personally NOT be comfortable with someone else trying to play an isolated version of the Moment/Big Bad Wolf as it is more suited to an event thing and still in many ways part of Rose and unwieldy to try to isolate separately. Osgood is the same way, both parts of her make up so much of how and WHO she is, that isolating one half isn't truly possible, nor recommended.
SO + 1 to Osgood having a mirror-self in all its oddity. Just my 2 cents as someone canon familiar & having RPed twins and everything else.
ALSO apologies but as a Who player... some additional clarity
In the case of Osgood vs. Osgood, this is not like a set of twins, but absolutely requires a single player, rather like Akito and Agito. Same brain, same experiences, except differing in the case of Ak/gito, same personality and voice. It's like a superhero disguise except in the case of Osgood, the disguise is the opposite. Given the rule about Ak/gito requiring the same body in order to keep it easier for other players to interact with, IRONICALLY I would suggest that it's easier to interact with Osgood having a double.
Osgood is an exceptional case to the zygons, BECAUSE of Osgood's extreme personality. She's so overpowering that she overtakes the zygon's individual personality and it becomes preoccupied/"possessed" by what Osgood wants. There are some other cases where this could happen, (such as with the clones including that of Amy, who were capable of being so convinced they were those they duplicated they were prejudiced against other clones) but Osgood is the only case for the zygons, which makes her extra difficult to play without her real duplicate purposely BECAUSE of how others treat her. She doesn't actually interact with herself, she only notices the ABSENCE of her other half. -> Something that would make for a more interesting character development event if Osgood (one) was ever killed, because even then the remaining Osgood would go into hiding (as aforementioned by her player) and fret about a zygon/human takeover until rescued/etc.
I know that's REALLY confusing sounding, and it's all VERY timey wimey, but basically, I'd rather Osgood could have her duo-part as still part of the one same person and player. It's sort of opposite how the Doctors are separate personalities that do in fact interact with each other, Osgood has no need of it because she is the same, with the same goals, same mind, same process of thoughts, and no change of mind. There's no need to talk to each other or interact, and indeed, they could not be played separately because every thought is the same and unlike twins, they aren't basically overcome by one identity. With the Doctor, it's different because he treats himself very differently and unlike Osgood, fights with himself, rather than having the same goals in mind, and indeed, each incarnation has a different thought process as well.
In my opinion, it's similar to how the Moment/Big Bad Wolf takes on Rose's personality and face, by borrowing the moment she rescues the Doctor, and then has the same goal in mind. I would personally NOT be comfortable with someone else trying to play an isolated version of the Moment/Big Bad Wolf as it is more suited to an event thing and still in many ways part of Rose and unwieldy to try to isolate separately. Osgood is the same way, both parts of her make up so much of how and WHO she is, that isolating one half isn't truly possible, nor recommended.
SO + 1 to Osgood having a mirror-self in all its oddity. Just my 2 cents as someone canon familiar & having RPed twins and everything else.