when do you think chaldea members will start dying?
Good question. If they are truly killing (no "oops I returned five seconds later" circumstances) their members (the ones with names and a sprite instead of those who are "disposable" names), it might come as soon as 6.5. If it counts as "main story" because Sion flagged Avalon would be the last (real) mission they can complete without losses. Spoilers.
I want Goredolf to make it to the ending, even confront U-Olga because he was an established parallel to the original Olgamarie, but (with Munierre), he has the biggest chance to die in 6.5, if anyone dies. Of course, it may not count because it could become a main interlude, however.... if it does, it will be him or his dynamic duo partner. I've always thought he was safe until Lostbelt 7 because of that Team Phoenix CE that was said to foreshadow a dinosaur adventure. But he's involved in the new Summer event (with a Summer-y sprite) that was a dinosaur adventure. There could be another, but I get the vibe of "Fake Vinci and Goredolf summer focus farewell" from the PV. It could get second thoughts once I read the event. When characters who have laid low like them during this are suddenly thrust into the spotlight after that death flag, it looks like a way to have "happy memories" before their endings. That's my impression. Goredolf ceased to be a comic relief person only in Olympus too when he expressed his desire to atone for the Chaldea invasion that happened when he took the mantle of director. In Avalon (or was it in other chapter? My memory is fuzzy), Guda says he is like a "father" to the group which is another death flag. He still makes the atmosphere lighter, despite not being fully comic relief anymore, which means he and Munierre (duo) are the first candidates to die to show "things gets serious!" His subplot and story might be connected to Koyanskaya too, and the other reason may be because he will appoint Guda, the "Last Director of Chaldea" that would also finish Guda's transformation as Romani's heir for their own seemly inevitability dead-end (which could or not happen, I must say the evidence is solid but FGO is a mobage). The white mystic code has yet to make an appearance and shares some similitude to Marisbury's old uniform and some high-ranked Chaldea officers. That's speculation, it could be something unrelated like "Rainforest survival mystic code." Still could make it to LB7, we’ll see.
As for Gran Cavallo (using her real name). She is dying and her profile and material spoil that. She lacks a Deus Ex Machina like Fou attached to her to spare her as happened with Mash, and she doesn't have a heroine role either. I mean this could still be prevented. She got a summer version only furthers her death flag. Nemo is able to transport people with the Storm Border also makes the Shadow Border not as pivotal as before. When she's dying? She is definitely surviving up Lostbelt 7 now her material expresses her desire to stab Rasputin in the back to avenge her maker and predecessor, Da Vinci. She could die anytime after Rasputin dies, or helping to kill Rasputin in that case (unless Nasu will be cruel and make her "shut down" unfulfilled).
Holmes is going to be an antagonist. The details of who he is to everyone's guess (will he be a side-antagonist like Douman relegated to a 0.5 chapter, or one of the main ones?), but it's already too transparent and set up. Pretender is probably his true class. Moriarty will return to help to defeat him, probably with Enkidu. I think he is probably that Servant who made it to Olympus and left because this is an open subplot that Nasu said would come back later. I suspected the Archer who left a message in Atlantis was him (using "Shinjuku" as his blurred alias or Tesla or they'll use Tesla as red herring later). The Munierre survival may be guaranteed up to this point if he is somehow involved with defeating Holmes (there was an odd moment with him in Enkidu's interlude).
Nemo and Sion "Chaldea members status" is a little less important and prominent. They can die anytime, they can also betray Chaldea at any time it happens. Or survive. Sion definitely flagged that there could be an attack on Wandering Sea despite how safe it sounds in Avalon (she stayed behind because they couldn't leave the headquarters unprotected and exposed with no one). However, I can't see them as part of the Fuyuki Singularity return expedition. So something has to happen.
This is my impression and wild guesses. They can change at any time.
