Hello,
I've made some new discoveries while working on this, the biggest one is that SDBG (link below) actually works for oVirt WebAdmin!
This means there's a viable alternative to existing GWT debug method, which doesn't restrict you to using an ancient (NPAPI-compliant) browser, while still being able to use Java IDE (Eclipse) as well as reaping the benefits of SDM code server (fast incremental recompiles).
If you're an oVirt UI maintainer, I highly suggest you to join this session, spend ~1 hour of your time and in return, get the knowledge to be more productive when dealing with our GWT code.
Regards,
Vojtech