Oh great lord of the interfaces and electrons - made it... it works - what a relief
So, what i did in a few short steps:
1) Reinstalled 2.2RC1 from scratch. eth0 is green eth 1 is red1, eth2 is unconfigured
2) created an additional uplink (uplink1) with eth2 - active/managed
3) told mainuplink to fire up uplink1 if itself fails. managed.
4) told uplink1 to fire up mainuplink if itself fails => uplinkeditor.cgi stalls
5) found 2 corrective rpms on efw-mantis, that i downloaded and installed
7) uplinkeditor does not stall anymore ! on problem less.
did a test - not working mainupllink does not fall to uplink1
9) deconfigured backuplink on uplink1 (no fall to mainuplink)
10) did a reboot
11) it works: when i disconnect the mainuplink, it automatically (after some time) takes uplink1
12) if the mainuplink gets back, it "routes" all traffic back through this interface.
After all i saw in efw-mantis, some bugs (uplinkseditor does not show activated backuplink - .js error etc..), are corrected, and i'm now convinced, that i they will hopefully soon flow into another public rc or maybe even a final...
Regards and thanks to HTH