Obviously, migrating from a Mac OS X 10.4.x system to a 10.7.2 is still possible provided you can use the target disk mode. I tried with an old iMac G3 (slot-loading, Mac OS X 10.4.x) and the transfer started via FireWire (target mode). I don't know what result to expect but at least it appears to be supported by Apple (see screenshot).
Personally, I would do it "by hand", it's neither difficult nor time-consuming.