Well, pairing Shirou with Rider instantly removes from play the two people who Sakura is most commonly paired with.
true but you asked the question
Well, yeah, because I wanted to pair Rider up with someone who isn't already paired up. It defeats the point if we just shuffle characters around without good reason, the idea is to pair us as many as possible....
Well, I can understand that, but in Rider's case pairing her with a girl makes a hell of a lot more sense than pairing her with a guy. Most of the girls are at best dubiously bisexual, whereas Rider is canonically close to lesbian.
that logic doesn't follow
It does when you also take into account the relative lack of guys.
and threesome illusion thing aside no canon instance of rider being interested in women has occurred
Ayako?
She also seems to be rather interested in Rin in HF True. Her being mostly interested in girls is universally accepted.
No, Rin is bisexual, Rider is lesbian with a side of Shirou.
see above.
I could argue the same about Rin, though. There is no canonical instance where Rin shows significant interest in another girl, aside from
maybe Saber in a few cases. Also, it's an unfair comparison because Rider shows up a lot less, especially in FSN.
point is the other girls would probably like being with characters other then Rider.
Well, sure, but there are only so many guys to go around. I mean, aside from Lancer, who I assume will be with Bazett, and Toshi, who else do we have left?