The graphics system on Lion allows for KEXTs (32 bit extensions) in drivers. There is an actual code wrapper that goes between the graphics card and the driver on Mountain Lion which is 64 bit hence no KEXT support.
That's exactly what you are talking about. Supporting 32 bit only hardware. If Apple had a 64 bit driver for your card it would run Mountain Lion. In fact it wouldn't shock me if a 64 bit Linux driver gets ported over and then ML does run.
No, I don't think you're right about this. As you say, the ATI x1900xt (the card in my Mac Pro) has windows 64-bit drivers. I've run one under Vista 64! Secondly, if what you are claiming as a major graphics change would be true, I could swap in a $50 graphic card into my Mac Pro and be fine to install ML. But I can't...It's more arbitrary than that.
Because you would be running the full featured samba and not the reduced functionality. Lion moved from Samba 2 to Apple's Samba clone. Ports has Samba 3.
You're claiming installing the Mac Port replaces the builtin smb functionality?
No its specs in terms of driver support are not inferior and that's where you are getting snagged.
EXACTLY. The keyword from your reply is: "support." This is where Apple is not willing to put in the effort. The hardware itself is fine. Apple is just not willing to do the support. Again, this situation is very different from 68k to PPC, or PPC to Intel. Deprecating old architectures makes sense. Deprecating powerful workstations -- while supporting inferior laptops -- just because you don't want to port a 64-bit driver that already exists for every other OS does not make sense. Blocking ML on a computer even if it has a fully upgraded, brand spanking new 2012 graphics card does not make sense.