Fighters being.. fighters and the experts of tactics and combat related skills I can see. However, I don't see them as knights. (that is more... Paladins and maybe CLs in my mind). I don't see them as the Heavy Armoured guys. Rather more likely light armour, chainmail, or even just leather, which allows them to use their various tricks, and not rely on merely "hit hard, and able to take hard hits". Things like the defense skill being more effective the lighter the armour and best with leather etc. Let other guilds rely on heavy armour, and fighters on their skills.

That they are not tinkers I agree with. Things like skinning and leather crafting, finding healing herbs and similar things of an "organic" nature I see as well within their field though. More barbarians or rangers than knights or mercenaries.