What makes you think users aren't changing the defaults on fidelity bonds if they want to? JM has always been a bit technical and I'd argue most of the active users know how to configure it. It's 1 setting in the config file that's part of all the other parameters that they need to set. Without the FB, a single maker can make as many offers as they have UTXOs for. An offer with a large bond is going to be more valuable to a taker than a offer without. Perhaps it may be helpful to allow easier configuration in JAM for less savvy users but I don't think forking it is necessary since it is ultimately up to the taker anyway.