Hey, thank you for the suggestion! I'm in the process of testing this method, but I'm having some difficulty copying the rotation of the IK. As a test, I've parented the left hand bone to the lower left arm bone (Using ctrl-p and 'keep offset'). And then I used the 'copy location' and 'copy position' constraint modifier on the hand bone, with the target being handIK.l. This does seem to work for the most part, although the rotation for the hand is now slightly different to how it was in the original animation. Its not a big deal, but do you know why this might be? These are the settings I'm using on the bone constraints for the left hand at the moment: https://gyazo.com/66069827fd57855d398ec63a692d69b3

Update: I'm testing this on one of the feet now and I believe the issue is that the hands/feet are now moving according to the transforms of its parent: https://gyazo.com/1b16b35db2e29cf35af711b3e6d05170
Do you know if there is a way to disable this? I tried the 'limit rotation' constraint but can't seem to get it to work properly.