Are you open to the concept of a new, non-canon class? Let me explain. I've worked in this a little, recently. 

[Hider=Explorer][i]
“...that’s one small step for man, one giant leap for mankind...”
[/i]
[b]EXTRA CLASS: EXPLORER
[/b]

It’s a well known fact that there exist many instances of Heroic Spirits recorded upon the Throne of Heroes that remain untouched by modern mages. The most common seven class containers are intended for combat and destruction and serve the purposes one would desire for a Servant nicely. Rare is the mighty warrior that would not find one of these potent containers suitable, but it remains an inarguable truth that there exist heroes who have carved their names into history for whom these containers are insufficient. 

For these servants, the containers of EXTRA classes must be prepared. Shielder. Gunner. Foreigner. These containers are sometimes utilized in summoning, but they are far from the only example. While rarely invoked due to their lack of a speciality in the sphere of direct combat, there exists the Container ‘Explorer’. 

While some members of this class have other suitable classes due to their exploits in life, several heroic spirits can only properly manifest using this container, limited to those people whose discoveries and journeys marked a notable turning point in human history. Servants of the Explorer class typically have higher than average agility and endurance attributes, reflecting the difficulty of the journeys they have made and survived, and their noble phantasms invoke not powerful mounts, weapons, or magecraft, but rather allow them to manifests the environments and situations they are most well known for conquering. While they do not excel in combat they are premier survivalists, able to walk away from situations and environments that even other servants would balk at, and their adaptability makes them dangerous to underestimate. 

Class skills for this class include Independent Action, as every member of this class has to some degree learned how to survive on minimal resources and support. They also universally have some rank of Pioneer of the Stars, as every member of this class has pushed humanities boundaries further in some way, having thrown themselves beyond the known world. 

Examples of Heroic Spirits who could fill this class container include Sacagawea, Lemuel Gulliver, Marco Polo, and Neil Armstrong. Existing servants who could also fulfil the criteria for this class include Francis Drake, Sanzang, and Astolfo.[/hider]

If you find the concept interesting I'd like to take this for a spin, with a servant from this class, alongside a master I have in mind. If you're not interested in this or find it to out there for how you envision your game progressing, I'm capable of respecting that, but nothing ventured nothing gained as they say. Asking never hurt ^^