Please show me how to print a lower case 6.
Are there line-of-sight issues
Yes, the satellites are low in the horizon. I'm in southern Norway, and most of the time I'm unable to take advantage of EGNOS (WAAS) unless I have clear view to the North Sea. However, there is an internet service calles SISNeT, which delives EGNOS signals to ground users. Likely to be a bit expensive...
You simply cannot stack lenses like that.
Well yes, you can: It's called afocal photography.
It seems to improve autofocus
Well, maybe improve accuracy in some cases, but the contrast detection AF of non-DSLRs is usually slower than phase detection AF of DSLRs. The very best CDAF is comparable with PDAF of average DSLRs, and then there are the sports cameras...
Have you tried a modern digital viewfinder? For example the VF of the Olympus EP2. I'd say it has enough resolution to not make a significant difference. It has 100% coverage (of course
Many large manufacturers of DSLR's, such as Canon and Sony, have started removing the mirrors from their prosumer-level camera's in exchange for sensors that can work in different modes.
Well, Canon (and Nikon) are still on the fence. Nikon may (or may not) present a mirrorless system camera at Photokina, Sony has their new NEX-system, then there's Olympus and Panasonic (micro four thirds), and yet another system, Samsung NX. Even Ricoh is jumping on the bandwagon, in their own idiosyncratic way.