Raimondi,
For ZI, it sounds like very attracting (M mount) to have a prestigue range finder camera. But the investment is a long way and huge.
For DSLR, as you does not have N mount or 645 mount lens, you should not have any burden to go on any particular brand. EOS sounds like a possible option as you have lots of C/Y lens.
To me, NDigital seems like a reasonable option (at least I could use my Contax 645 lens along with NAM-1 adapter) but my worry is it would be a potential bomb of the after sales services of digital camera particular the community is not a big group.
Even worse as it is already stop production for a while, user experience is not so good.
If the price of NDigital could be lower like HK$15000
(it won't happen...), then I would go to taste the power of Full Frame CCD but to avoid low light shooting (noise problem).
I understand the dominant factor of the optical lens is not so important in Digital Camera. Electronic processing and conversion on image capture does take significant role.
For traditional camera, optical factor is a MUST.
My two cents.....