You're right, KRS' are, like the next series of K bikes, scarce. I don't know how many were produced, but I suspect that the two series have the same "problem": owners keep them. My '03 is hardly the latest word in bikes in general, and K's in particular. Aside from the K1600 (sadly, hell will probably freeze over before SWMBO will concede a change of bikes), I really don't feel a need to move sideways into a fast tourer.
Options are the FJR or Concours (had a C10 version, liked it very much but no ABS, and a willingness to let gas dribble into the cylinders). That last leads to hydraulicing one or more cylinders which, since gas effectively won't compress that leads to bent piston rods. Sadly, BTDT. Sold the bike for peanuts to some who could replace the motor. I don't see the VFR 800 as a true tourer so much as a long day ride bike for sport touring. See YouTube videos by Richy Vida, particularly his current series about four VFR's brought to the US from the UK. The fifth member of the group brought his GS. The four VFR riders constantly complain about being knackered at the end of the day(s). Point made, I think.
I think the ST has very good points. But extended two-up isn't one of them. Particularly when carrying cargo (camping stuff, clothes, etc.) on long trips.
Any BMW maintenance is spendy. It's just how it goes. That said, generally, I think the KRS is generally good on not a needing constant diet of parts and techs' TLC. But... if the ABS modulator lets go, the replacement, to BMW specs is EFFIN' SPENDY ($2K USD). Typically the servo's motor fails. In my case the seals went. Either way, effectively no brakes. There are two alternatives. There is a company that rebuilds the modulators. AFAIK
the work is good and the rebuilt unit is reliable. Some people report by-passing ABS altogether. That's stupid. No other description applies, save to add adjectives such as effin', etc.
The problem with the rebuilt modulators is any dealer probably won't touch a rebuilt unit. The process involves pulling the modulator, sending it out before reinstalling it. This opens up Plan B for maintenance. There are some good non-dealers who did work that's every bit as good as most dealers, and maybe better. And some a trash. Finding a good garage takes some research, but could well be time well spent.
Another main area of woe is the rear end. The details of any failure mode are, IMHO, unclear and range from outright failure (bad unit with defective parts shot from day 1) to poor maintenance (change the rear-end oil as you would your motor oil). Neither of these are guaranteed to happen, it's just they're ones most discussed.
The one must-do: the fuel line quick-disconnects (QD's). The stock QD's are made from plastic. Some have failed, the rest will fail. Period. The good news is there are after-market sources for replacement metal QD's. If the PO put them in (often happens, but not always), good. If not, do it like it happened yesterday. Really. If one lets go, at best you have an out-of-gas moment. At worst, pray the fire department arrives in time. 'Nuff said. You can look through the opening on the right side the tupperware, where the motor sticks out. You can see one of the two fittings. If it's white, it's plastic. If it's silver, no worries.
Things to change... First, resist the urge to change anything
until you lived with the bike for at least 500-1000 miles. What seems odd on day 1 will probably be just fine later. That includes dropping foot pegs, mucking with handlebar mounts, and other ergo-destroying things. BMW really did get the ergos right. If you feel an over-whelming need to do something, add a small air horn. The stock horn really is sad. But almost any bike's stock horn is sad. You can add reflective sheets to the rear end of the bags. Won't hurt, might help, and there are some good, ready-cut kits available.
The stock headlight just doesn't seem to get it done. I don't know why BMW punted on this one. Your only options are live with it, or move to HID lighting. LED's are not an option. There simply isn't enough space to handle to heatsinks behand the lamps - no way. BTDT have $50 tied up unless stuff. The low beam HID will swap without a lot of fuss. You will need to drill a 1 1/8" hole in the dust cover, to take the dust seal from the HID, but otherwise it's plug&play. The high beam H3 lamp requires the existing socket be seriously altered to hold the lamp. Think hard about that. Two things that simpy don't fly: 1) changing the wiring, desirable as that is, really won't fix much. The headlight internal wiring precludes a real fix. For the hot supply wiring or the grounding. BTDT, saved a ton of useless effort. 2) High wattage (100W, 80W) lamps will ultimately melt the headlight reflector. It's 100% plastic. The added heat load will, sooner or later begin to soften and... best of luck finding a replacement. BTDT, see $50 useless lamps above - $10 for a 100W H3. You can, of course, all manner of external lights. I did that on my C10 and found the odd shadows on the road, from the mounting location available, just didn't get it done. But live with the bike for a while before starting to mess with the lighting. The changes all take some effort.