I wouldn't want Link changed too much or else it would feel weird. If they happened to make him female or another rather large cosmetic change in one game just for funsies I wouldn't have a problem with it cus it would still be the "Link" of that game, but a fully customizable player character every game would make them feel less like actual Zelda games imo. If they made him more customizable, I would want it to be in-game options like in BOTW, maybe have a hair salon clothing shops etc so you can switch things up later in the game like in Pokemon, but choosing at the beginning wouldnt feel right to me.