This a little bit premature, but, when designing these things, usually the system board layout has to work with the design of the shell that the board will inhabit.
Some of the things that I recall about the current thinking for the body are:
1) Initial design will be a clamshell case like the SL-Cxx00 series
2) A 4" transreflective display 640x480 minimum
3) A hardware keyboard built in (just to be clear)
4) 1 CF Slot, CFIO capable - this is a no...
5) SD Slot, SDIO capable
6) 1 USB port, not sure if Mini or normal, Client or Host, or combined
7) 1 HDMI port for video out
8) 1 Audio out
9) 1 Audio in
10) 1 Camera
11) 1 Power input (again just to be clear)
12) Easy access to battery(ies)
13) Easy access to reset button
14) A Rocker switch (because the Z has it)
15) A Cancel and an OK button (because the Z has it)
16) A Power On/Suspend/Off button (no reason can't work like PC)
17) A speaker
18) A microphone
19) External antenna connection(s)
20) GSM Identity card access
21) a bunch of LEDs (HD, POWER, BT, WIFI, ...)
22) Fingerprint reader
Boy, that's alot of stuff.....
However, there can never be enough... Some things I'd like to see in additon are:
1) 2 CF externally accessable. No internal HD, I'd like to be able to easily switch out HD's. This one will be very hard to accomplish, because of the realestate needed.
2) Both the USB Host and Client ports available in the full sized version.
3) I'd like to see 2 SD slots.
4) Maybe stereo speakers?
The keyboard should have some application keys some of which could be lighted different colors, to indicate on/off status, ie turn on bluetooth, or wi-fi. The rest of the keyboard should be able to be backlit.
--edit-- added in the fingerprint reader, and make comment about CF slot