I fixed some issues in yast2-network-2.17.16 and did some tests and the result is : it works fine!
1 - Boot into any already installed linux, download kernel & initrd, create /boot/grub/menu.lst entry - some documentation here, also possible to use miniISO
2 - Into bootloader pass install=$custom_or_public_NETWORK_repository option
3 - Unplug your wired card
4 - With this setup will Linuxrc try to use your wireless network card to connect network repository. There are some dialogs to specify ESSID, WEP/WPA and sharedkey
5 - In case of connection succeed, do installation as usual (via wireless ;-))
6 - Before first reboot this network setup will be saved as persistent (into /etc/sysconfig/network/ifcfg-wlan0)
7 - During next boot (2nd stage of installation) wireless network is automatically up and you can finish installation