A lot of the comments question the use case but I think your story captures the ideal use case, a hybrid C++ / web app where you want to or need to share some of the functionality between web / c++ sides
It's not a bad way to build a web interface for a C++ application that needs to be configured over an intranet. It makes tying "click on a button on a web site" to "run an administrator action on my application" very easy, and you can use your Qt muscle memory to lay out a simple admin interface with relatively little mucking about.
You can do all that with CGI scripts or whatever, but if you already have a bunch of C++ running on the server it isn't nuts to use Wt to build your CRUDy admin interface.
In addition, I have used the templating in the library and it works really well. Let the UI/UX people do their thing and get the best performing back end.
