Maybe instead of a saddle, placing metal on it, enables it to "fuse" the metal with it's skin, making natural armor similar to shadowmane once a player gives it metal. This could also be shown in making the raptor more metallic material(texture) as it is given more metal. Maybe when attacked, the metal breaks off a little of becomes useless, so you need to keep giving it more metal to keep it's armor values topped off. Also, with more armor, could come more weight or a buff that slows you, decreases turn radius, jump height, ECT., making a decision between a tanky raptor and a speedy and agile raptor. I mean it doesn't make much sense for a flaming raptor to have a hide saddle