There may be possible problems for the cost of borrowing among the northern and southern euro, but this could be solved by their independent values against other currencies, and inter-dependent borrowing. Since both are parts of the same EU, borrowing at times of crisis may even become easier than assumed. This is because the southern Euro can borrow loans from northern Euro at mutually acceptable rates, though imposed and governed by the parent EU. It seems to be a good option in terms of saving its gradual death.
The best possible option seems to be the establishment of the southern Euro which is different from the northern one, and may even be devalued due to its lower economic prosperity. The using of domestic currency for domestic transactions alongside the Euro for international transactions looks ideal, because it makes possible a smooth and gradual penetration in the EU market and provides the southern euro opportunity to be recognized for its individual position. This may allow it to integrate faster because all are almost at same economic levels and binding them may not be difficult. The southern Euro can trade independently and create its own niche in international market, allowing it to be a new entity in global trade agreements that suit their core competencies. The exchange of Euro between the EU may be more frequent and without a risk of mispricing risks, leading to more intra-EU investments according to their internal strengths in different sectors of the economy.