Please you probably copied it off me
I've had this idea ever since complaints started coming about Troop Training, but great minds think alike.
I actually saw it as a solution to the Tiger Ace concerns as well. Basically you can just replace it with a normal Tiger, but now they have a greater ability to reach Tiger Ace status through their own actions, and replace it if needed.
Another novel solution: No XP boost, just unlock vet 5 for all units when using that doctrine