The producer at this point doesn't seem like a bad person minus that bait face they gave him at the end of 133, so I'd be really surprised if Shinobu refuses to let Fumi do the seggs scene and risks losing his position over it. Just running thru the different possibilities, I have no clue what will happen and don't favor any one in particular.
In the end the resolution could be a lot simpler but right now the possibilities are : 1) Fumi herself does it after eventually convincing Shinobu, 2) A back up double actress ( conveniently Sakura?) is called in, 3) Shinobu loses his position over a creative difference with producer-san. 4) Both the movie and Sakura's offer sub-plots are sidelined for the finale plot out of the left field.
1) happening is good for ShiFumi even though it sounds bad, it means the trust between them has gone up, but with this scenario I don't see how Sakura steps into the picture. 2) seems plasuible with a dash of plot convenience because the og timeline of events make no indication of Sakura getting an offer of Shinobu movie, still it would be hard to properly flesh this out over two chapters imo unless they work a miracle and go speed. 3) Is extremely unlikely because it's another bad end for Shinobu, chance is prety close to zero but not necessarily nonzero from how I see things. 4) I don't even know what the new plot would be but the reason for this would be to just immediately combine both perspectives of the MCs back into one and devote the remaining pages to entirely focusing on untangling the conflicts remaining.