I think if I understand you correctly then the short answer is: Not easily.

The idea above is good, but I'm not sure you can use an expression to populate the target of a sub report element, at least not without using some VB code (please correct me if I'm wrong, it'll be useful for me to know!). Do your sub reports have parameters of their own? If so you'd also need to set those as well, and it rapidly gets very complicated.

What is the wider context around trying to execute reports in this way? If it's the case that certain users always want the same set of reports, you could try using subscriptions against individual reports to email them out once a day, for example. If you're trying to build some sort of interactive dashboard that allows the user to change what metrics they see, then SSRS isn't the best tool for that.