Uncle Dave, I couldn't agree with you more! I just bought my first arranger keyboard because I needed it for the job I'll have this summer (summer here lasts 6 months, so it worths the investement). I am originaly a piano player, and used keyboards for some extra sounds live, or for sequencing songs. I was totaly against arranger "things" because anyone could sound good on them regardless of his skills.
Now I have one, I see that they can be very useful instruments, but still I try to use the arranger part the least I can. I do exactly what you do. Manual bass on the left, drums and piano or guitar or whatever suits on the right. But the owner of the place where I play wants to have the impression that 10 musicians are playing(eventhough he's paying only 3! ) and is very satisfied when he has it! So, I must use the "big band" to satisfy him. Stil, whenever I have the oportunity, I turn everything off and use only piano which makes me feel I'm playing on my ground.