Makes some massive headway with the real config section, have got all code re-delegated to using it and have migrated the baserest config to the core project, all configs will be shared out of the UmbracoConfiguration singleton, now to get the unit tests all wired up and using mocks for the most part.

src/Umbraco.Core/Configuration/BaseRest/ExtensionElementCollection.cs

@@ -0,0 +1,70 @@
+using System;
+using System.Collections.Generic;
+using System.Configuration;
+
+namespace Umbraco.Core.Configuration.BaseRest
+{
+    public interface IExtensionsCollection : IEnumerable<IExtension>
+    {
+        IExtension this[string index] { get; }
+    }
+
+	[ConfigurationCollection(typeof(ExtensionElement), CollectionType = ConfigurationElementCollectionType.BasicMapAlternate)]
+    internal class ExtensionElementCollection : ConfigurationElementCollection, IExtensionsCollection
+	{
+		const string KeyExtension = "extension";
+
+		public override ConfigurationElementCollectionType CollectionType
+		{
+			get { return ConfigurationElementCollectionType.BasicMapAlternate; }
+		}
+
+		protected override string ElementName
+		{
+			get { return KeyExtension; }
+		}
+
+		protected override bool IsElementName(string elementName)
+		{
+			return elementName.Equals(KeyExtension, StringComparison.InvariantCultureIgnoreCase);
+		}
+
+		protected override ConfigurationElement CreateNewElement()
+		{
+			return new ExtensionElement();
+		}
+
+		protected override object GetElementKey(ConfigurationElement element)
+		{
+			return ((ExtensionElement)element).Alias;
+		}
+
+		public override bool IsReadOnly()
+		{
+			return false;
+		}
+
+		new public ExtensionElement this[string index]
+		{
+			get { return (ExtensionElement)BaseGet(index); }
+		}
+
+        IEnumerator<IExtension> IEnumerable<IExtension>.GetEnumerator()
+        {
+            for (var i = 0; i < Count; i++)
+            {
+                yield return BaseGet(i) as IExtension;
+            }
+        }
+
+        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
+        {
+            return GetEnumerator();
+        }
+
+        IExtension IExtensionsCollection.this[string index]
+        {
+            get { return this[index]; }
+        }
+    }
+}