Thank you for using our services.
We are happy to see that you have managed to sort this one out. I was going to suggest an identical approach. To create two themes that share the same appearance/styles. One would be for English content and in this theme you would just specify in the menu skin that the direction is left to right. And the opposite for the second theme which would be applied to Arabic content pages.
If you have more questions, please feel free to contact us.
the Telerik team