Steve.. I think for an arranger with extensive sequencing and editing capabilities, the Roland G-70/E-80(used one) or the Korg Pa3X/Pa2X Pro(used) could be considered. Both of these arrangers have microscopic editing possible.I haven`t used either of these but have heard users mention the flexibility in editing available for these arrangers. In all arrangers you mentioned, there are fills. In addition there are dedicated pad buttons and you could assign a custom fill(drum roll etc.)to each of these pads and moreover I think that these can also be triggered through foot pedals(not sure on this though)connected to the keyboard... so really no need to take your hands of the guitar.

Moreover, you could even consider using a combination of an arranger keyboard and a computer based Digital Audio Workstation(DAW) software. That would mean a lot of flexibility at a good price but then a lot of work with eyes staring at the screen and carrying that laptop wherever you gig

I am just a hobbyist musician.. I`m sure many experts here could guide you on exactly what you`re looking for.
Good Luck.