VisualSVN and class libraries not in the working copy root
Found the best answers here:
Referenced Projects
Sometimes it is useful to construct a working copy that is made out of a number of different checkouts. For example, you may want different subdirectories to come from different locations in a repository, or perhaps from different repositories altogether. If you want every user to have the same layout, you can define the svn:externals properties.
And here:
Include a common sub-project
Sometimes you will want to include another project within your working copy, perhaps some library code. You don't want to make a duplicate of this code in your repository because then you would lose connection with the original (and maintained) code. Or maybe you have several projects which share core code. There are at least 3 ways of dealing with this.
I understand it's been more than ten years since you asked this question, but I am glad to tell you that there was progress in implementing support for multiple working copies in the VisualSVN plug-in.
VisualSVN 7.1 and 6.5 support multiple working copies within a single solution. The new functionality is available to Visual Studio 2019 and 2017 users.
Download the latest VisualSVN builds from the main download page. Please also see the article KB7: Using Multiple Working Copies in VisualSVN.