So some Master Servant pairs (or rough equivalents) have to go through Part 1 of FGO, up through Solomon. They get back-up from Chaldea in the forms of rayshifts, logistics, and information gathering, but don't have access to the FATE summoning system. However, the Servant doesn't require magical energy from the Master to operate at full power.
Scenario 1: Shirou and Arturia
Scenario 2: Shiki and Arcuied
Scenario 3: Seig and Astolfo
Scenario 4: Aoko and Soujuuro
Scenario 5: Ayaka and Arthur
Bonus round: Gun god gets dropped in
All characters have access to their strongest form under normal conditions (meaning no unsealed Excalibur or Archetype Earth outside of situations they would actually be called in)
Scenario 1: Shirou and Arturia
Scenario 2: Shiki and Arcuied
Scenario 3: Seig and Astolfo
Scenario 4: Aoko and Soujuuro
Scenario 5: Ayaka and Arthur
Bonus round: Gun god gets dropped in
All characters have access to their strongest form under normal conditions (meaning no unsealed Excalibur or Archetype Earth outside of situations they would actually be called in)