Can you describe why having a single subversion revision number across multiple projects is a problem for you?
There are some legitimate advantages to using a single repository for all of your projects. The biggest one being that you're probably better able to control changes between common code in multiple projects.
If you have a problem with the concept of a single incrementing subversion revision number across multiple projects now, have you considered the situation where you branch one of your projects? (remembering that a normal branch will also have a globally incrementing subversion revision number)
It sounds like you're trying to use the repository revision number as part of the build or release number?
If that's the case perhaps you could consider implementing a different build numbering scheme for your project/s that can then be associated with the subversion revision number.
Such an association can be made by using a convention of creating branches with the release number and putting the subversion revision in the comment for the branch.
Some schemes were discussed in this question