If you want to do this entirely via customization you can add your own action and render the required tables. If you are using TaskFormTemplate the actionmodel is defined in NetMarkets-actionModels.xml file as shown below
<model name="taskFormTemplateDetails" resourceBundle="wt.workflow.worklist.worklistResource">
<action name="taskFormTemplate" type="workitem"/>
You can add a custom action and build a table. To fetch the data you can navigate from workitem > wfprocess > CR > Affected Objects.
As I understood you already have a custom Task Template. You can actually create a custom taglib, the taglib class should call a Jsp page having MVC call to custom affected item table builder and this custom tag can be included in the Task template for ECN. This will display the affected table on all the task using the custom Task template.
Please let me know incase you need help with respect to the code,
I followed the same steps- created a jsp having mvc call to a custom table builder containing the affected objects. And gave a call to this JSP in my taskform template and it worked. Thanks Aditya and Bhushan.