There is a need for both shorter and longer term plans. A short term plan could be a euro bond that has differential costs to different countries when they use it. The costs should be lower than a higher risk country's own bond implies but higher or lower than the costs of the euro bond. How much higher or lower should be determined by the member countries collectively.
A differential design imposes a real cost to those countries that have taken too much risks or ill disciplined fiscally that contributed to their current fiscal predicaments.
It will provide a solution to those countries risking of default with lower cost of financing.
It will also lower the costs of those other countries that bail out those high risk countries.
Politically it would be beneficial for both debt and credit countries within the euro zone.
A longer term plan could be further strengthening the original requirement by the euro constitution/agreement.
A really long term or permanent plan is fiscal integration. But it will take time for the conditions to be right.