Ryan was chosen as vice-presidential running mate precisely because he HAS a plan. As head of the House Budget Committee he drafted and submitted a budget that would balance the budget over a short period of time with minimal pain, provided that it is enacted soon.
In contrast, the House and Senate have failed to pass a real budget for the entire time that Obama has been in office. The most recent budget submitted by President Obama was not serious, and received precisely zero votes.
Romney could have taken the conventional approach and chosen a running mate based upon demographics, in order to win over more voters. Instead he chose someone based upon the major issue that is facing this country at this juncture in history.