I think this is do-able.
You need to modify the xml in UWL administration or upload a new xml with a high priority.
Try using IviewLauncher, that will launch your transaction iview on click of workitems based on a particular TS.
<Action name="launchIView" handler="IViewLauncher">
<Properties>
<Property name="iview" value="ROLES://portal_content/com.sap.pct/every_user/general/iViews/myDemoIView"/>
</Properties>
</Action>
https://help.sap.com/saphelp_nw04/helpdata/en/b1/cc1357eead454bb144face4a66be7d/content.htm
Ankur...
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