While slightly more squishy than the other options, all of them are morphing your arm into something not remotely human, healthy, or appealing.
I spent some time following the video links and think I have a better handle on this. It the order of operations for Spycraft/Mastercraft tonics look like feats - you should be adding them at the rate your class/career level normally allow a feat to be acquired. You could then add a rule that basically lets you get a tonic feat early... but it messes you up pretty darn bad until a selectable feat slot opens up, and then it automatically takes that slot over. Running 2 tonics ahead of the curve being dramically worse, and 3 tonic/feats ahead probably not being something that should be allowed.