Did you ever think you might be thinking too far ahead? How about finding out first what they want the system to do (if it's not a direct port) and then pick the UI and tools based on their requirements. The last system lasted 40 years and I'll bet it lasted that long because they could find at least a minimum of support for the OS and software (and by now it's very cheap to support because they don't change anything.) What ever system you come up with, if it's based on Windows then I guarantee it won't last that long. How many Windows 3.1 applications do you see still being used? You can get very fancy with the UI but in the end it just needs to be functional. It will be the back-end data that lives on way after the front end gets replaced so that design needs to be very solid. After all that's probably what this project is anyway. A new front end and their backlog / wishlist of new functionality because they probably will want the old data ported.

I worked on a project to replace a 40 year old manufacturing system several years ago. We used C#.net WinForms and SQL with MS reporting services. It worked out pretty good and saved the company millions.

Be very careful with the interviews. You will get scope creep and then everyone will be expecting something different.

This might be a long shot but check this out. http://grubletrang.com/Software.aspx?app=PowerPrompt[^]