The RS has the first frame mounted fairing used on a production bike. That being said, as lovely as the bike is, they made the error of allowing the bars to swing INSIDE the fairing. That pretty much limits your choice of bars and bar-end-accessories. Anything that increases the bar-end swing radius is verboten. Even the use of bar "set back mounts" becomes questionable. And yes, with the stock mirrors your body does block the view of what's right behind you.

The best mirror work around I've seen is to buy a cheap set of stubby black handlebar mirrors with the M14 thread. Then disassemble the stock mirrors and tap the hexagonal hole in the OEM mirror base to M14. (You can also buy spare mirror bases on eBay.) This gives just enough added width to see behind you. And black mirrors on the black mirror base won't catch anyone's eye as a glaringly out-of-place modification. 

Since no bar-end anything is allowed with the RS fairing, the best "cruise control" device becomes the stock BMW friction screw that you can fit yourself. This thumbscrew had to be removed from production bikes after 1978, but BMW wisely left it where you could buy the thumbscrew and install it yourself in less than 1 minute. If you need to reduce the spring pressure, then there are low pressure return springs offered.

If you use a bar end mirror there is an unconventional option. Get a  new hand grip and cut the hole for the mirror undersized. The tighter, rubber on rubber fit can hold the throttle and allow the rider to relax the grip occasionally.