I'm also a bit skeptical about the contract implementation, but from a plot perspective it doesn't matter very much. Even with Excalibur sealed and her left hand disabled, Saber outclasses Lancer. Even without the self-Geis scroll, Kayneth has no other option for evading Kiritsugu. It was probably still a bad writing decision to add a plot hole simply to make Kiritsugu look badass.
(A better subversion, IMO, would have been to have Kiritsugu not inherit the Emiya family crest -- which is what it looks like from the perspective of Fate/Zero anyway. Then the self-Geis fails for a reason Kayneth may have genuinely not known.)
The bigger WTF, in my mind, is why Saber's left hand was injured at all. That whole sequence required her to hold the Idiot Ball twice. Where did she ever get the idea that Servants only have one Noble Phantasm? And since when does her magical armor slow her down? Argh....
I largely agree with your points.
Further, Kiritsugu explains his goal as eliminating master & servant simultaneously, but this seems entirely unnecessary. You should prefer to eliminate a servant first, so it can't contract with another master or act as a free agent, and also eliminate a master so they can't hang around and fight you or contract with a spare servant - but there's no need to do them simultaneously in the same battle, and with Kayneth there was even less need: he was completely crippled physically & magically, so he could neither fig...
This is the monthly thread for posting media of various types that you've found that you enjoy. I find that exposure to LW ideas makes me less likely to enjoy some entertainment media that is otherwise quite popular, and finding media recommended by LWers is a good way to mitigate this. Post what you're reading, listening to, watching, and your opinion of it. Post recommendations to blogs. Post whatever media you feel like discussing! To see previous recommendations, check out the older threads.
Rules: