Is it possible to make efficient queries that use the complete regular expression feature set.
If not Microsoft really should consider that feature.
I think we can see from the new types in SQL Server 2008 (hierarchyid, geo-spatial) that if Microsoft do add this it will come in the form of a SQL CLR Assembly
If you are able to install Assemblies into your database you could roll your own by creating a new Database\SQL Server project in Visual Studio - this will allow you to make a new Trigger / UDF / Stored Proc / Aggregate or UDT. You could import System.Text.RegularExpressions into the class and go from there.
Hope this helps