Can I tell bindingRedirect to always use the latest available version?
Unfortunately, the answer to this is no. See the bindingRedirect element on MSDN.
To quote:
oldVersion: Required attribute.
Specifies the version of the assembly that was originally requested. The format of an assembly version number is major.minor.build.revision. Valid values for each part of this version number are 0 to 65535.
You can also specify a range of versions in the following format: n.n.n.n - n.n.n.n
newVersion: Required attribute. Specifies the version of the assembly to use instead of the originally requested version in the format: n.n.n.n
This value can specify an earlier version than oldVersion.