I'm happy to report that my hack to the sony-laptop kernel module works. We were able yesterday to make the first UMTS data connection with my wifes' Z21, using HSOconnect on openSUSE 11.1. Her detailed description of installing openSUSE 11.1 on the Z21 can be found here, you can also download the source code of the sony-laptop.ko. It's a very rough first version, don't expect packages or inclusion into mainline kernels soon. Still, it gets you where you want.
Loading the module will generate a new file /sys/devices/platform/sony-laptop/snc_wwanpower, you can switch the modem power with "echo 1" and "echo 0".
I'm still working on the graphic card problem, hopefully I'll have a solution soon.