This question came up during a Commander tournament/league where no one present was aware Shahrazad is banned. =/

I can see how MTR 2.5 implies that additional turns only apply to the current game. (Though it could be much clearer.) However, there is nothing I can see in the MTR or CR.subgames suggesting that one can't start a subgame.

How does one deal with a subgame created during additional turns?

The oddball rules situations that arise from Shahrazad may have had something to do with it being banned in all formats. Or maybe the Rules Manager (at the time) just got tired of me whining about having to answer Shahrazad questions … and then argue that the answer was, in fact, the Answer. :)

But, on a serious vein, this fact remains: Shahrazad is banned in all Sanctioned formats. There won't be any ‘O’fficial answers for such questions.

If a play group chooses to allow it, then they also choose to allow these odd situations to occur. It's kind of like when you auto-click through the license agreements, so you can play the latest & greatest Call of Duty - you accept all those stipulations without ever really reading them. And, one of those might read “Shahrazad must not be included in any question. Ever.”

OK, I couldn't remain serious. But, seriously? Sorry, no answer exists.

d:^D