I was able to convert a "flexible" panel into an omega compatible region simply by adding the CSS class
grid-4 to the panel container in the panel's CSS settings. The result is a collapsible omega grid on the front end. However, the downside is that in the backend, the columns are not visible (you just see stacked regions in the backend).
You could use
grid-12 in a similar manner to accomplish this. You might then need to add some CSS to cancel out the default "flexible" panel stuff:
You'd then need to adjust
It's not a perfect solution, but it worked for me so I figured I'd share this because it's helped me get responsive panels in a very simple omega-based theme.