I saw this article over on IT-Analysis on converting legacy applications by Tel Hudson of Bloor. I tried to post it as a comment but their CAPTCHA system is broken so I kept getting errors. Hopefully they will fix it! Anyway, here's what I was going to say:
I think replacing a whole legacy systems, even in an automated fashion, is unlikely to solve the problems. Most legacy systems suffer from lots of changes because the business rules they implement change often. Replacing one form of legacy code with another is not terribly helpful.
I blogged on using rules to enhance legacy applications (http://www.edmblog.com/weblog/2006/01/enhancing_legac.html) and to improve application maintenance (http://www.ebizq.net/blogs/decision_management/2006/10/using_decision_technologies_to.php) on my blogs.