Futuwwa often charge without orders, as with Ghazi, and this can be quite devastating. I totally agree with your criticisms of them, i.e. their poor defence etc, but I enjoy trying to utilise units that have specific strengths and weaknesses. The trick with Futuwwa is to deploy them so that rhe enemy are focusing their missile fire on your better armoured units (Saracens and Turcoman foot). So the Futuwwa should be bringing up the rear.

The big difference between JA and these others is the elite status. This means you won't see them running along with the non elite units. IIRC there is no other elite pure missile foot unit?

Nizari are like souped up Ghazi with bows - minus the AP bonus. The problem there is the defence, as with Ghazi it's extremely poor. Even Futtuwa have better defence, which makes them more useful if they get stuck in melee.