Can you add an issue on our issuetracker to track this feature request?
The project paths that are stored in the solution will be per user overridable in the near future. (Best guess +- January 2009). This is part of the enlistment support planned for some time. It is recommended to share the solution file (especially on websites as the .sln actually contains the project references). AnkhSVN can’t redesign the Visual Studio project model, but we will try to implement optional parts of the SCC specification with some more user configuration options than other products. (e.g. allow customizing most user project paths, while TFS and VSS only allow editting enlist enabled projects).
Please contact me via the email@example.com list if you have further questions.