I cannot seem to be able to find a way to assign an ASM security policy to an iApps Service, can someone please let me know how? Thanks.
Take a look at the Sharepoint template, it is implemented in there: https://devcentral.f5.com/wiki/iApp.Microsoft-SharePoint-2013-iApp-Template.ashx
You can look at the implementation section and pull out the ASM piece to include in your own iApp.
If you need additional guidance, we can take it apart together.
You can assign an ASM policy to a VS implemented with an Application Services by changing the properties of de Application Service unchecking "Strict Updates".
Doing this you can make any change to the VS directly.
Of course, if you disable strict updates and then reconfigure the iapp, all ASM policy will go away and have to be manually created anew.