Crashbars that really protect the bike - something like the Metal Mule or Wild @ Heart bars for the 800GS. Best ones I've seen yet on an S10 were from South Africa. They were custom made - post 1365-66 at http://www.wilddog.za.net/forum/inde...pic=23116.1360
If yuo can come up with something close to this that doesn't require cutting the panels, I'd buy it in a heartbeat. The bars should also allow access for side panel removal.
A bashplate you can actually "bash"! I think the S10 has plate mounting on the oil pan - same as my 800GS. This does not work well in my experience. Perhaps some way of having the rear of the plate mount on the footpeg brackets? (I think Hepco and Becker had this idea for the S10 on their Intermot bike) Anything to keep pressure off the oil pan, or at least diffuse the pressure as much as possible.
Handguards, unless Barkbuster Storms will work.
Tail rack/plate with some carefully thought out slots for bungees and straps.
A strong pannier rack with good lateral cross bracing to support the rear of the rack frame. Ideally integrated with the top/tail plate so that you can open your panniers even with a top case. (Unlike Yamaha's set up).
While I'm dreaming, perhaps an auxiliary fuel cell set up like the World Crosser concept Tenere.
Raising links, and even better a front end raising kit. I would love a bit more ground clearance.
Fastway F5 size and style footpegs.
On the electrical side, again, while I'm dreaming: a handlebar mounted "info" control so that you can work your way through the bike info stats without taking your hands off the bars. Bonus points if it has an ABS "off" switch. (Thinking of the BMW handlebar layout for this)
Heated grip kit without the massive and ugly controller, or better yet, a kit with a high/medium/low switch on the handlebar
Dash shelf to mount heated grip controller, extra 12V/accessory sockets, etc.
Front fender raising kit
Above dash vibration dampened GPS mount so that you keep your eyes on the road rather than looking down at the bars.
Kaoko throttle lock
That's all I can think of for the moment.