Hi,
The codes can be synchronized using SVN as described here:
http://www.esenthel.com/?id=doc#Synchronizing_Codes
So the only problem lies with synchronizing Assets.
For new assets that aren't yet available in previous game releases, you can easily solve the problem by creating a "Folder" element, you can call it for example "Work in Progress", and right-click and "disable publishing".
Keep inside that folder all new elements that are still in development.
Once assets get ready for release from this folder, you can move it to another folder, for example called "Ready for Testing".
As for modifying existing assets, that are present in previous releases, that depends on the type of the asset.
For some assets, you can "Copy" that asset to a new temporary element, also disable its publishing, and add "for next version" to its name. Once element becomes ready for release, you could update the original element to be the same as the modified version.
Or another idea, is to connect to Esenthel Server and synchronize the changes, only when updating the element to latest version / changes has been completed fully.
As for storing Project's "Data" file in text format, I will send you a private message about the cost.
Thank you