1. Why would Dany be afraid to attempt an assassination because of one personal guard? Why would any of her advisors be like "can't do that, the mountain might get em
"
2. That twitter poster was right, Dany has sent in solders secretly into a city before. Both in Yunkai and at
Casterly Rock. It makes no sense why she wouldn't try what has worked before. At the very least to open the gates, if not to sneak into the Red Keep for an attempt to remove Cersei before a full on assault.
3. Dany's advisors happen to know THE MOST of anyone living about the secret passage ways in KL. Tyrion and Varys know all about the city, inside and out. Davos too apparently. Tyrion would have to either feign ignorance (making himself look more useless and or like a traitor) or tell Dany how they could sneak into the city, which would have made for good drama. And by all accounts, Varys would be all about taking out a single malevolent monarch to install another one. Why wasn't this even mentioned as a possibility?
4. We've had Ramsay and his 20 good men infiltrate Stannis' camp, we've had Bronn sneak into Winterfell with a crossbow, we've had Daario sneak into Dany's camp with multiple weapons, we've had Tyrion smuggle himself into KL, we've had Theon and co sneak onto Eurons ships to rescue Yara, and a ton more instances where characters accomplish something by sneaking. This wasn't suggested once? The only options was this contrived "Kill everybody or kill nobody" scenario?
5. ARYA IS A FACELESS MAN. They have a faceless man, who happens to be on her way to assassinate Cersei anyway. It's like everyone has forgotten that she just ended the apocalypse by defeating death itself.
Whether or not these assassins would have succeeded in their hit job is irrelevant. My point is why wasn't it at the very least considered? It seemed like the most straightforward compromise between the two extremes they kept putting on the table (sack the city vs diplomacy)