Well, this Mordred is no weaker than Kairi!Mordred because even though Law is not a magus, as a Sin-Eater he is ridiculously efficient at maintaining her.
This. Basically Law is an excellent master due to being a Sin-Eater. It is both easier for Mordred to manifest around him and Plasm is a very effective power source for her. She could easily take on Rider with Law supporting her, and Sakura is not immune to bullets. She also can't come back from the dead.
Well, no, she's not immune to bullets, although I do suspect she has magic that would make normal bullets somewhat useless against her (since most magi do).
Anyway, it's kind-of irrelevant, because I have no desire to find out, and any attempt to force me into such a fight and kill Rider or Sakura will cause me to invoke the "no kill" thing.
Show me something that says it does.
Because I have never seen anything to suggest that, and it sort of makes no sense.
Show me something that says my argument is not the case.
I'm tired of digging through Complete Materials every time you or Mike are spouting fanon. If you can find me something that suggests EMIYA's strength is entirely his own, I'll believe you.
Brah, you are entirely entitled to expect proof if you want us to convince you of something, but if you want to convince us, then you are the one who needs to produce the proof.