He never should have taken it off in the first place! It totally destroyed the aura. Imagine Darth Vader had taken off his helmet in ANH after a few minutes!
I agree with you that, in an ideal world, the mask should’ve stayed on. But, given what happened with Kylo by the end of TFA, there was no way for him to go back to being the mysterious, formidable masked warrior he was at the start of TFA. The illusion was gone. So, the best option for the following two films would’ve been to just ditch the mask and try to develop Kylo without it.