Mitiempo,I agree with the above with the exception of the Blue Seas 8686. For one he only has 1 bank. For another, if he did have 2 banks that switch lacks flexibility to start from either bank, combine being its only option. Combining a battery that is incapable of engine starting with a charged bank makes no sense.
I would go to one on/off switch and from there to both the panel and starter. If a second bank is planned for the future a 1,2,both switch makes sense.
I agree on the 8686 -- it's not really the best idea. The problem is, there isn't a great solution. A bolt-in would be nice, and the 8686 comes close, but it's really not there. And it reflects Blue Seas aversion to the 1-2-b switch, as you point out. I've nearly completed a rather complex "panel board" for my boat, which includes 3 100A surface breakers (one from each battery fuse, one from the switch) feeding 2 small fuse panels (one on each battery breaker) that feed a total of NINE "vampire" (always on) loads. It's a mess, albeit one that I think is neat and orderly. With all the required fusing and distribution near the battery, it's not possible to do what the 8686 wants to do. They sell another panel, an on-off with 8 breakers, that might be possible to make work. But it comes pre-loaded with 15A breakers, and they won't work for your alternator or your house load, requiring changing out two of the breakers at least.
Oh, it is enough to make your head spin!
Harry