title: Change web.config belonging to Mandatory WiX feature based on another optional feature
body: <p>In our WiX installer we've had a mandatory feature which installs all our websites.  Up till now this was enough, but now we have an optional feature that not only contains a single file, but will also require changes to the web.config if it's not installed.</p>
  
  <p>Since the web.config is already installed as part of the mandatory feature, is there any way to only do the XmlFile parts to remove sections as a part of the optional feature?  I've tried duplicating the web.config Components, but I end up getting a whole load of ICE30 errors.</p>