First of all, let me say that the concept you’ve come up with is brilliant.
However, as someone who only writes in C++ when I am in a really machocistic mood, I feel very let down by the fact that the FrontPanel API is in effect only accessible by C++ programmers.
I would personally rather have seen that C++ programmers were treated on an equal footing with, say, Delphi programmers, by being given access to the base functionality in the form of a DLL or a COM interface.
This would not in any way preclude you from supplying a C++ class as you do at the moment, it would just be a class built upon a common (DLL?) platform available to all.
I toyed with the idea of creating the DLL myself, until I noticed that a couple of functions return std::string. Duh! At that point it just seemed like far too much hassle…
Just my $0.02 worth…