Sweet. 
Regarding characters from other settings showing up in the story, will they have the same personalities as they did in their original settings? Like if a character is a tsundere in her original story, she's a tsundere in this story as well?  
Hm these quest areas are essentially in alternate dimension or something right? Like you get transported somewhere else essentially? 
I could imagine this possibly happening to Shirou somewhere: 
 
Image has a Pharaoh, Sphinx, Anubis, Mummies, Khepri, Girtablilu, & Sandworm. 
Liliraune would be another fun monstergirl for him to run into on a quest: 
 
Hm regarding his Projection abilities here, any swords outside of Ea or Excalibur might Shirou jot be able to Project here? 
And would Gil here be FemGil?