@swift240
Let me see if I can answer you "Swiftly" :-)
1) 8Mb ChipRAM standard (upgradable to 32mb via 72pin SIMM)
2) 68060 as standard (removable) and all chips removable
3) 4 SIMM slots on the Mobo (up to 512mb RAM) or maybe PC133 RAM
4) S-Video OUT as standard with the ability to force PAL into NTSC always 100% ON or NTSC to PAL for UK users
5) a seperate VGA out with the output already scan doubled while still maintianing S-Video OUT in NTSC via the RGB and S-Video Ports
6) AAA Chipset (or at least an entirely new Gfx mode thats compatible with AGA and ECS but displays 16 Million on WB. It should be real cheap to do this as one can maybe Pay ATI for the rights on one of their old NTSC chipsets or even Faroudja (preferably)
7) 24bit sound chips with MP3 decoder x4 (Can decode 4 MP3 at once)

2 Gigabyte sized Kickstart ROM or at least capable to add this. (Why? so you can put more software in it, like DVD display menu, VCD Menu, AudioCD menu.....(Think CD32 or Sony PSOne) WinAMP type Visuals in the ROM so one can play CD with Visuals and control them as well as add your own Gfx.....You have No idea how ESSENTIAL this is!
9) USB 2.0 as standard.......or Ethernet Port or 32bit CardBus instead of PCMCIA
10) SATA Harddrive port instead as well as the IDE one (Buffered)
Thats my Top Ten list in that exact order for an A600/A1200