 So, you made an awesome rig for an awesome character and you want to modify that rig for a different character. Not a problem. As you can see, we have a rigged character. But let's say we wanted to modify this existing rig to this guy right here. They share a similar structure, so instead of recreating a new rig from scratch it probably makes more sense to re-use an old one. Right now the commando has no rig attached to it, so the first thing that we gotta do is clean the target. Get rid of everything on the target that has no weight paint data that you need to transfer. So, all of the armor and weapons are going to be parented, so we really only need the core base body. Once we've cleaned the target, go to the character you want to transfer and make sure that it's not parented to anything and that none of the parts on it are attached to any armature. Then select all, copy, then go to the other blender file and paste it to the target file. Alright, now the character is here but it's not attached to any skeleton. Before we attach it, click the rig and tab to edit mode and start deleting any bones that are not going to be used for the new character. For example, the new character has no fingers, so we can go ahead and delete those bones. Make sure that you have x-axis symmetry turned on because that will make sure that everything that we do on one side will automatically be mirrored to the other. Now we're just going to go and reposition the bones to make sure that their new position makes more sense in relation to the new character. So obviously the bones on the legs should be at the center, we'll also look at the knee joints to make sure that they're positioned correctly, then quickly check them in pose mode to make sure the IK still works, probably move the arms and shoulders down a little bit, check the elbow to make sure it's in a good place, shorten the arms a bit, and I actually forgot about the toes. Let's go ahead and make sure the toes are where they should be. Okay, and check the spine real quick. The neck and the head look like they're relatively alright, okay. And once you're done adjusting the proportions, tab the pose mode and check to make sure that all the IKs and functions still work. Looks like they do, so now that everything is ready, we gotta attach the character to the skeleton. So, click the character, shift click the rig, control P and pick automatic weights. Now usually that will do the trick. You can fine tune the weights if you want, but if you want to transfer the exact same weight paint data from the previous body to the new body, click the original body, shift click the new one, go to weight paint mode, and under weights, transfer weights. Change vertex mapping to nearest face interpolated, ray radius to 5, and source layer to by name. And you're done. The weights from the first body have now been transferred to the new body. From here you just parent and weight paint the armor or weapons the same way you normally would. So, that's how you modify an old rig to a new character. Hope that helps and as always hope you have a fantastic day and I'll see you around.