I think of it like this,..........As a singer all I need is "my band with me" which includes all the other style parts & two backup singers (VH)....I use approx 50 styles which can cover any genre of songs I need all custom tweaked and edited for my way of playing including mostly the same 8 sounds, some layered, in OTS, STS, etc, in upper 1 & 2 sounds which rarely change as each member of the band would in real live performance playing "their" instruments. I can understand that "Instrumentalist players" need more sounds but that's not the case for me. I also have no need for charts or lyrics mostly which allows more freedom to play off the cuff the way I want it to sound. Works for me using One registration per song. Anything that goes beyond the workings of the arranger in style mode I create a custom Mp3 backing track to play & sing over as too many parts are needed for the arrangement I prefer.
An arranger is a multifaceted tool to be used in many many ways!