Instead, Kohl's government mistakenly imposed an absolutely unaffordable welfare- state structure, including too-heavy taxes, on the former East Germany, making impossible the kind of resurgence West Germany experienced after Erhard's reforms.
In other words the solution is the same as it ever was, and may be as politically impossible as ever it was: the Germany government would need to provide official underwriting for the funds borrowed by the Italian, Spanish and other eurozone governments, what is known as mutualisation of borrowing, to reduce their borrowing costs and provide assurance of credit supply.