Well I wonder who led the Qunicies after Bach fell, I wonder if there were some splinter cells, and "Bach's Blood or Power" Mutated after generations. Or Bach wasn't the only first Qunicy... Maybe he had a brother, that carried a different kind of Qunicy powers, because I don't see Bach's Qunicies shooting arrows.
^ Hm ? Fach used a Quincy Arrow on Yamamoto and Bach himself even created a Bow in mid-air and then shot an Arrow, which he picked up as sword and then cut Yamamoto in half...
Ishida family always seemed strange to me, they seemed as if they were the ones that lead and chose the Quincy's future, especially seeing as they named themselves "Last Quincy" (even though Souken obviously communicated with SRs and probably was in the Vanderich Empire a few times). Of course it's possible that they are more of a backup, the last family that has to rebuild the Quincy Kingdom in case it was wiped out or something ?
It's also worth mentioning that the Ishida family has it's own philosophy, also regarding the Quincy Powers (Seeing as Souken was teaching both Ryuken and Uryu). They perceive the Quincy Arrow as the basic of the basics, as well as the hardest art to master for a Quincy (basically all Quincy can use the Quincy Arrow, but almost none of them are masters of it). The Quincy Final Mode is even a quintessence of it, the art of One-Hit-Sure-Kill, since in it a Quincy can shot an arrow so strong that it not only annihilates the target, but also burns out the user.
For example, Opie, also known as the J-ritter, mentions that Uryu's arrow should have been more powerful than his own, which suggests that it is still a valuable ability worth recognition.
Currently there are only 2 Quincy's known to be capable of destroying a Bankai, Uryu and Hashvalth, which are seemingly within the top 3 of the SR.
Oh right, I forgot to mention that the SR that activated their Holy Complete Forms so far (Opie and the Gun Quincy) showcased that they posses a special Arrow Technique in those forms, so the Quincy Arrow seems to be still a very important element of the Quincy's battle power.
I totally forgot about that, I just find it weird that the SR all have special abilities almost like Shinigamis do, Instead of using a zanpakuto they can use there "Soul" without a weapon. I'm still puzzled on how Tier, was defeated by Bach. Also being able to use someone's Bankai which takes years to learn, "Regarding Ichigo" so effectively. I think when it comes down to it, I feel the Quncies were actually apart of SS, and Apart of Bach's Royal Family... and we don't know much about the Noble Houses.