I know what you mean Earl, I can relate. I'm a home hobbyist. But for me the workflow would be:

-Make a set list
-Obtain the music, either paper or MIDI
-Transpose to preferred key and simplify if necessary (some chord progressions are just too hard for me to play in real time without making a mistake!)
-Try to find a style that goes well with the song
-Practice! Orchestration really don't matter at this point, as long as it's pleasant enough to listen to
-If a song still seems too difficult, drop it for a while and move on to the next one.
-Only after I get really good at a song with the default sounds/style, THEN I'll create a new registration BANK for that song (Roland calls it a User Program Group)
-I create one registration entry for each section of the song that involves any kind of voice or control change. So far I haven't done a song with two different styles, but it's very possible.
-Annotate the score (either paper or digital) with a reminder to change registrations

Bottom line: no matter how good the panel is laid out, I'm not quick enough to change multiple controls within a couple seconds while I'm playing. Most models have the ability to change OTS with variation, or vice-versa, and that's a good starting point. But it's more foolproof to create a custom registration. The downside to my approach is that once the song is fully evolved, it will always sound the same way. I recently got a BK-9 and I haven't yet worked out how to use the "favorite" tones to give myself some variety when I get bored.

Bottom line, YES it's easy to get distratcted fiddling and not even get through a practice set. For me it's a fun way to while away an evening, but there's a reason I don't quit my day job!!