Please consider implementing the use case you are looking for using a LivePage.
Please be warned that this could stop working with some of the future versions of Polarion ALM, because it uses an internal API. But something similar will be definitely possible (e.g. custom macros). Including content from servlets is only possible if no authentication is required.
Copy and paste the content of macro.txt into your Wiki page. Use #includeExternal("<Servers base url>""<Path to content that should be included>")
Use #includeExternal("""polarion/...") to include servlets hosted on the Polarion server.