As the flexible builder in panels is not responsive, and the provided the layouts are not flexible.
Is that possible to provide a flexible builder with responsive?
The flexible builder in panels can create percentage based layouts which are, by their very nature, flexible. I don't see the problem.
flexible means when there're 2 horizontal columns 'A | B', when A is missing, B would float to the position.
While responsive is when the browser/screen becomes small, 'A | B' would appear vertically to suit the browser/screen -- this is unavailable currently.
isnt that panels related?
I think it is panels related, maybe a plugin or something that allows for building panels as grid-4, grid-8 etc... so they fit within the Omega grid nicely. At the moment I can't see any point in having to make a panels layout first, and then go into your site and use it as a variant, it's pretty inflexible.
You could achieve the same in under half the time just using the Omega appearance settings to specify the different regions but you don't get to use the drag and drop of panels or being able to quickly add different elements to the page via the UI.
Context/delta kind of addresses this but not fully and not with the same number of options panels provides. Still looking for a happy medium myself.
Finally there's a solution: http://drupal.org/project/layout
Drupal is a registered trademark of Dries Buytaert.