I've always been baffled at how the supposed king of England, rules of countless knights and the Round Table, has zero commands skills and allows herself to be controlled by a 17 year old Shirou. I'd expect the King Arthur to be more commanding and inspiring, rather than just being a "stab stab slash"-type
Eh, there's plenty of potential explanations for that. The obvious one is that it just doesn't come up in the scope of the series -- Saber seems to
strongly be a more "lead by example" (the example, largely, being wide scale unstoppable mass slaughter) than... posing and speeches and similar such silliness. Lacking a situation where there's major geopolitical shenanigans (and, iirc, the series actually pretty strongly insinuates that Saber was
kinda' terrible at that sort of thing -- great at inspiring loyalty in a select few, less great at managing a nation), she has no need for such things anyway and it just... doesn't happen.
To boot, Saber's working with something like 3-4 other people (most of them, y'know, basically civilians) at once, at the most, and is completely lacking in what would be her normal supporting infrastructure. It's entirely possible she kicks several kinds of inspirational ass when she's got her full field command on hand, but I don't think we ever see anything along those lines.
Also: She's totally got B class charisma (And remember, something like E class charisma would have put her on par with normal maximal human capability). Which basically means that the only reason we don't see her diplomance the surrounding nations into her thrall is that
Nasu she didn't want to
write that story.
Though something like rejiggering the conflict into something like a modern day Game of Thrones might be interesting, if it weren't for the fact that
the Clocktower would probably fuckmurder every single one of them if they tried to pull overt geopolitical shenanigans while involving magecraft.
Point the second could be
the grail fucking with her head -- it shoves japanese and a number of modern skills into her skull, and iirc there's a certain degree of insinuation that the same process gives all the servants something of a nudge towards playing along with the war. Plus she's under the threat of the command seals, which is pretty limiting on her actions.
Her working with shirou is pretty easy to explain. Dude's got better info, is the only thing keeping her around for very long, and is generally working towards the exact same goal she is. No real reasons to clash all that hard, and it's not like they're entirely without interpersonal conflict. Plus the two of them just happen to get along pretty well.
* Frumple performs the eyebrow waggle of not-so-vague innuendo. *... mitigating circumstances, basically. A whole heaping pile of mitigating circumstances.