That sounds like quite a good idea Gareth - I'll probably explore that. It's not that I can see nothing behind but you have to tuck your elbows in to be sure of what's lurking, instead of just riding in a natural position and that split second of movement could be the difference of being safe or 'scooped up'. The mirror bodies are fixed (but can be folded in like they can on cars) the mirror glasses can be swivelled in their housings but even at the full extent of outward movement, they come up against the housings.
The master cylinders have the usual blanked off threaded holes - so something could be attached there. An otherwise very well thought out machine, let down by this one important thing.
Ian