Just make the styles your own.....edit them, rerrcord parts,swap parts,change sounds, efx,etc,make it exactly what you want after all it's an arranger!!!!....there are no bad styles but tbere are bad musicians...dont blame the styles....
Perhaps you cannot blame the styles themselves, but it is the technology, voices and programming of the brand that dictates the quality or realism of the style.
I have auditioned different brand arrangers in the past. Yamaha technology, vast resource style/multipad libraries, and best support system makes Yamaha my best choice for my arranging and live performance needs.
My last Ketron product I tried was the Audya. The audio style parts were really well done and authentic sounding, however the rest of the style parts and most of the regular voices were very GM2ish.
The present Korg PA2X, though almost catching up to the Tyros 5, the styles are thin, uninspiring, and with lack of resources towards arranging needs could become quite boring over time.
Yamaha in the other hand with present Sweet, Mega, SA, SA2, and audio drum parts within the style technology and great programming, plus huge resources, gives you limitless potential to your arranger needs.
The unique Yamaha programming that goes into their present styles is mostly interchangeable to be used in the Multipad parts or vice-versa. Korg or Ketron styles converted to Yamaha don't translate as well or can be as good as Yamaha styles because the style part "programming" (eg. Mega/SA) is missing. Just as Yamaha styles don't translate that well into other brand arrangers, because the Mega, SA, SA2 technology or programming is obviously not compatible.
My solution is to stick with the Yamaha brand, with the top quality voices, styles, multipads, and the large resources and support proven over the years. All my custom work must be compatible or up-gradable to the next model arranger. I wouldn't have the selection and creativity switching brands.
Aidan, the Tyros 4 is a nice board. surprised you didn't go for at least a used Tyros 5-76, for piano playing. Maybe if you like the Tyros 4 and how well it works as an arranger, maybe upgrade to a Tyros 5-76 in the near future. You will love the Organ World and Ensemble features, especially with added MIDI bass pedals.
If you assign your forth Ensemble voice to your MIDI bass pedal channel, you actually can create a five part independent voice ensemble. Truly remarkable for classical and church use. A lead solo instrument (with legato-4 Voice Incremental - from highest), 1st Violin, 2nd Violin, Cello, Bass Cello (with bass pedals), as an example custom ensemble voice. Ensemble is truly amazing, works with styles, and assignable to OTS positions. Many SA2 Ensemble lead voices to choose from.
The choir and vocal effects introduced on the Tyros 4 and carried over and improved on the Tyros 5 are second to none, including within the styles and multipads.
There is an inherent bias against the Yamaha brand in this forum, so not the greatest place for unbiased advice, but you have to try yourself what works for you.
Regards, Marcus