There are systems and there are systems. I think most of us on this forum are not countenancing the mindless things such as "horse names with an x in them or horses with four white socks." (Hey, could one of you database guys check those two out for me?)
The kind of approach to selecting (and possibly even backing) horses that I have in mind when I use the word "system" is in fact just an automation of a logical selection method. That selection method would probably only consist of the same criteria that any form analyst would use.