I can confirm you that you will not be able to get the Risks and Issues for out of the box IDEA object instances.
As per the best practices followed by the Project Management, Ideas should not face any risks and issues unless they are converted into a project. That is why, it is not included there I guess.
However, you can add a subobject and see if that somehow solves the purpose, by somehow. Again, this is just a "may be" workaround considering your requirement. Hope that helps.