Old_Fart_3269
hey if he wants more skills, maybe he should alter his hatsu like he did in the chapter before leaving for heavens arena in the hotel, He altered it to a larger "shady antique shop" if he finds an empty space, he can use more nen to change what it offers. like maybe he can make something like "shady education center" or "shady dojo" or if he wants raw power from enhancing his body. "shady alchemy apothecary"
why do you need a way to stop his growth, I personally would want to be "ready" by the time the "main story" continues. You could have given him some kind of hatsu that stops him from using a specific type of nen and after the time is up he develops a nen in that department. during that time he can focus on the other types. Or once every 7 days was maybe a little too often? (maybe evolve it later to increase quality?)