Charge for it. Seriously.
Discussion
We accomplish our custom features by putting our own service in front of Strfry instead of trying to modify strfry constantly to fit our needs. First, we aren’t C++ devs but more importantly the reason Strfry is so performant is because of the thoughtful design decisions Doug made. Wouldn’t take long for us to destroy that if we started messing with the architecture.
That’s the way I would approach this project too.