I don't know why it would be such a problem.
They are going to make the game work with controllers anyway (albeit, not soon, I think), and a lot of similar games have had manual movement, at least on consoles for most of them.
Dragon Age, Original Sin, Torment, Pillars of Eternity, Baldur's Gate, Dark Alliance, Diablo, Disco Elysium, etc.
Trying to play BG3 origins with zoomed in camera I found it to be troublesome - items didn't register properly from low angle, and there was no distance from which I could interact with them (I would try to click on an item, and istead the character would go to the door behind two doors. I don't think it is impossible, but most likely both camera settings (top down and zoomed in) would benefit from differet systems of item interaction. I remember DA:O having the same issue, though that game has been far less interactive then BG3. Of course, I cannot comment and what is and isn't feasable.
