"I only need maybe 10 styles and be able to play almost any song."
I only ever tweak from those I like the best, and never found the need, or desire, to create a style.
I have about 50 styles that I created using "Style Assembly" that are the basis of most of my tunes. These styles have the Intros converted into playable Variations and/or stop/fills and comprise the usual 8 Beat, 16 Beat, Rock Ballad, 6/8 Ballad, Waltz, Swing Waltz, Jazz Ballad, Big Band etc., and all are unique in some way from the factory styles.
I try to avoid using "song specific" styles...that's why the instrument we play is called an "arranger", so I try to put my own spin, or "arrangement", on a tune if possible.
I also have a collection of "donor" styles; styles that have unique strumming, arpeggios, phrases, pads, bass lines, percussion tracks, and I draw from these to use in creating something fresh, but still having a recognizable stamp on it.
"FreePlay" styles, both my own, and Yamaha's versions, are a nice change from drum pattern based arrangements.
I've never considered using styles a crutch...they're part of the art, and my palette of backing sound colors can range from the basics to a full blown orchestra, depending on my mood and/or what I am trying to present to the listener.
Many years of playing the Electone organ and not using styles, but simply a drum track, bass pedals and left hand chording/phrasing, has taught me to be expressive with the very basics, but I also like the both the freedom and restrictions of playing within/around a style.
We don't have to sound like someone else who has the same make or model arranger keyboard...sometimes, all it takes is a bit of exploring into the instrument's style creator (even a simple "re-voicing")and a little imagination.
Ian