Let's see,
I towered a CD32/SX32 once, had a few technical issues.
CD32 motherboard dimensions, approximately 285 x 150 mm by 20 mm high.
SX32 pro, 140 x 180 mm by 65 mm high at back panel. PCB + HDD, 30 mm.
My CD32/SX32 runs WB 3.5 fine, do not have WB 3.9 so can not try that.
It should wok with an IDE CD-ROM, you will need an IDE buffer though as the SX32 IDE port is not buffered properly.
My SX32 Pro, 030/50 MHz + FPU + HDD uses 2.19 Amperes @ 5V and 0.077Amperes @ 12V. Probably a bit too much for a battery.
The trickiest thing will be interfacing to an LCD display, as mentioned previously.
Oh the great website with CD32 tech into is:
http://www.ianstedman.co.uk/CD32/CD32_intro.html
See ya!