A shield overhaul would be nice, but I think increasing force field is more of a sloppy way to combat the problem. It comes with its own inherent problems as well, like protecting players from hits from behind or hits on the horse. As long as the shield protects from head to foot and a bit to the sides thats ok. Maybe increase the Length on some.
Main thing for me is giving more players access to shields that don't gimp them in some way. Often the shear weight of the things make them unattractive to take as a backup unless your main role includes holding a shield. Its often a lot better to simply judge when players will release a shot and dodge to the side, and you need movement speed for that. Deploying the shield makes you a sitting duck if there are ranged on more than one side, they get destroyed too fast (especially if you have 1-2 skill shield, but still with better ones too), and there is a good chance a xbower will simply crush straight through it. If players take points away from their main role for a support item they should really get better protection from ranged with it rather than simply weaken their main role. Shields become more useful towards the end of the round though when you are forced to engaged ranged. Thats when i'll take a shield usually if i find one on the floor. Before then its just too much of a detraction from you fulfilling your main role imo.
Not sure of the best solution..I still think simply having fewer ranged would be better than forcing everyone to becoming like a turtle. Reducing ammo counts would help, or make it so you can't loot more ammo from the field