Your web app will use a different project / .exe sharing the source code of your current desktop app; you will deploy this exe on the various production servers you mean to install.
Updating a FiC.exe to a production server is fully automated - with fast upload capabilities, you could support building your whole source code into a single FiC.exe
If not, you can also deploy separately the various components you presently have.
We would just need to test that calling a *.app (DO ... *.app) is possible from within a VFP.exe COM server.
Otherwise, instantiating classes from within a separate *.app should definitely be OK.
In fact, a VFP.exe COM server runs like any other *.exe, except Windows COM layer launches it.
HTH,