Culture shift with Ottos - too early cultural union

[Robert de Bruce]

i started an Otto run to just finish several achievements I haven't done yet which can be done by culture shifting. My original plan was to Otto-> Arabia (for Arabian Coffee) -> Persia (for this is Persia) -> Greece (It's all Greek to me). Yes, I could achieve all of them in another way, but for example I did Shahanshah the patch before This is Persia came out, so I don't want to do it again.
Usually this should be no problem. Unfortunately, i oversaw the changed mechanic (no longer a decision to culture shift, haven't done it for quite a while) and used the Istanbul decision to become an empire. This gave me a cultural union for all levantine cultures, which means i can't promote them, which means I can't make them primary culture. And I also can't change the order of my culture shifts, because forming Persia or Greece is forbidden for the Ottos.
Is there another way than doing a multiple shift, for example first to greek, then to syrian, then to persian, then back to greek for achievement?
Since I thought first I needed to culture convert a lot I picked influence and religious as ideas. So I could instead also convert all my turkish primary culture provinces to another one. Do i change my primary culture when the original one doesn't exist anymore?
It's already 1532, so I wouldn't like to restart if any possible.

 

[TheMeInTeam]

Romania, Croatia, or even a Maghrebi nation --> anything else you want should still work.

If you go super late and switch to rev republic to delete all estates you could in principle go full rainbow forming everything from Croatia to Greece to Arabia to Mughals to Manchu/Yuan to Italy then finish as Austria or something. It just depends how far you want to take it.