I've never had a problem with KGC steal.
Also, Yanfly Engine Melody + GB Production's BEM addons + KGC steal works flawlessly.
But you're probably going to stick with Tankentai (can't understand why, though. It's unwieldy and I've never seen anyone do anything interesting with it, so either its limited to what you get, or people just aren't being that creative with the tool).
Again, if you ever think about dropping Tankentai, the YEM/GB Productions/KGC steal
combo works without a hitch. Not to mention that YEM is a billion times more flexible than Tankentai. Neither Yanfly or Yami are supporting it anymore, but I've managed to fix every bug I've come across myself so far (and add a few new features for my game, easy since Yanfly's coding is organized I can find what I need/learn from his genius).
If you want help with KGC steal, I can answer any questions/give you a working script. If you're getting errors, it might not be the script's fault, but a compatibility issue (probably with Tankentai, I hear its not very friendly with other scripts).