Great for your customers if they are so deep in IT knowledge (what I doubt), but its not for all customers in the world. Besides, you can do all the above goals you mentioned, with Xbase++ and add-on tools in Xbase++, using only one technology: Xbase++. What is the most important for the customers is the end result. If you like you can integrate other technologies into Xbase++, I believe you read Otto's work with PHP, what I implement too. As I recall, you are also against FiveWin and WinDev, because you don't want to start from scratch when you have achieved so much in Xbase++. And why would you? You already do the great work in the great way in Xbase++.(Our) Customer nowadays are looking for highly scalable, multi-platform, safe and easy-to-use applications. Integration and scalability are demanded, it must be device-independent and good looking. Data driven, excellent looking, fast and reliable.

Anyway, Xbase++ is only one option amongst the many others, its up to you what you will use, not on the customers. When you get sick and go to a doctor, the doctor will determine your therapy, not you.