On all phones there is a file called /data/custom.bin. On my phone it contains expert/se on your phone it will say something else. This information is used by the custcopy commands in init.rc that copies wpa_supplicant.conf from /system to /data.
So you could make cust directories for all possible custom.bin files or you could work yourself around the custcopy. I choosed the latter. Look in my init.rc and /system/bin/userinit.sh and you'll see how it's done.
Just extract the kernel from my boot.img and pack it up with your initrd and it should work. The U8100 and the U8120 uses the same kernel config.
Or use my boot.img as it is and copy my /system/bin/userinit.sh. You may (or may not) want to modify it first but that way you'll get both overclocking and wifi on all models fixed at the same time. I also think I put the wpa_supplicant.conf in /system/wifi but you'll know for sure if you look at userinit.sh.
Let me know if you get stuck.
Oh, yes, one more thing, my boot.img assumes that autorun.iso is stored in /system/cdrom/autorun.iso (init.rc symlinks it to /data/cdrom/autorun.iso)