As a Nautilus player I don't think there's much of a reason to change the way Dredge Line in its current state. The only times where this would actually help is if you hook onto terrain near the enemy team where you wouldn't want to go (especially under turret) or you want to cast your abilities before you take your Dredge Line.
The former will never intentionally happen unless you miss your Q onto an enemy champion, and even there it adds a degree of mastery to Nautilus in lining up your Dredge Line. To engage, you would want to line up the Dredge Line such that it will most likely hit an enemy champion, and if it doesn't it gets you close enough to the enemy champion that you can still engage, while if you want to make a pick without fully committing you would want to aim it such that it will likely hit its target, but doesn't hit the nearest form of terrain.
The latter will likely not happen because there's rarely a time where you would want to lodge into terrain and cast spells in your current location. If you need to peel for an ally you won't use Dredge Line away from the target, if you want to engage you won't cast spells before Dredge Line (except Titan's Wrath during the pull, which you can already do), so there's really no reason to change it.
I also can't help to think that this would make his Q significantly more clunky for Nautilus players like myself, who have gotten used to playing with a Q that automatically travels to the wall, and would also remove some of the plays based around getting hit by the enemy's CC abilities but timing your Dredge Line before getting hit that you hit the wall in the middle of getting hit (the most prominent example being Blitzcrank's Rocket Grab, which gets completely nullified if you time it right).
