Just wanted to drop a note that Ian and I are working on the next version of IWeb.
IWeb 04.00.00 will use Windows Communication Foundation (WCF) and require that you have ASP.NET 3.0 or higher installed (For IWeb 03.00.00 you only need ASP.NET 2.0 installed).
Using WCF we will be able to allow you to expose any method from your custom module as web services method and still use the extensive IWeb security configuration screen to set granular access to those methods.
You will be able to write those methods in any ASP.NET language and you will not have to actually add the methods to IWeb. IWeb will "discover" that the methods exist (because you will use a partial class).
We anticipate a release sometime in 2nd quarter of 2008.