Well if you are looking at slinging it over your shoulder then forget 76/88 key keyboards. Even my Motif 6 with 61 unweighted keys would be as heavy as I'd want hanging off my shoulder.
I'd definately consider using the JV1080 with the expansion board and an external controller. That would be a relatively inexpensive way to to it.
When you talk about wanting an arpeggiator how were you thinking you'd synchronize the tempo of that to the rest of your band?
[This message has been edited by Nigel (edited 09-07-2007).]