With dragging, you need to drag in one direction, otherwise you station will be in the wrong place
You mean when you want to make an existing platform longer? Yes, if you enlongate a station by dragging and drag in the opposite direction, you will get platforms on the other side. I attached an image to display what it would look like, if that is indeed what you mean.
However, just like with ways, the player would see a preview before he ends the drag, so he knows beforehand that the station would be the wrong way around. And he has two ways of building it the desired way, either by just clicking single tiles (the current behaviour would not change in that regards) or dragging the other direction - since the platforms only get buildt when you end the click, they can all connect to the existing station.
And a dragging station tool with the current button will require that when stopping the same tile always a station will be built (even in the in the wrong orietnation) or you would not be able to build a station whenever you mouse move a single pixel.
Exactly, if you end the click on the same tile you started the click, the current behaviour will do what it does and create a station tile that is aligned to existing station tiles, and if there are no neighbouring tiles it's just the standard rotation. Nothing wrong with that.
Not to mention that you need to be able to drag within the same tile in order to control orientation of a single tile stations.
No, you just can't orientate a single tile station by dragging. Which would typically be stations for aircrafts, ships and cars, where platform orientation hardly matters, wheras all kinds of tracks where it actually matters seldom use single-tile stations.
My concern here is finding the function and usability.
Since dragging is something players already do and new players will probably try, the behaviour with the orientation will be seen and is simple enough to be understood if attention is paid. Functionality that requires CTRL will hardly be found.
Usability-wise look at the efficiency of the current method with map rotation:
It's either a mouseclick (opening the menu that includes the rotation button - this is optional) a doubleclick on the map rotation, and a doubleclick again once you are done - or you use the shortcut key four times.
If you implement the same is with extensions, you have to press control and click (two actions) and click again on the rotation you want. So it's at best as efficient, but if shortcuts exist or the rotation button is already visible less efficient, than the current method.
It IS better than map rotation if you want to have all platforms on the same side, as Vladki suggested, since that's currently not possible at all (in a useful way) - but if you don't want that, which is more likely, you'd need an additional click on the station icon in the menu to get rid of the locked rotation.
Using drag to orient the station does not need any additional clicks at all, thus it's argueable more efficient then either method.
Of course it's still the hardest to implement, so I don't expect it to be done, but that's because there is higher implementation cost for more gain, not because there would be no gain.