Double click would be a click tax for a lot of players. What you actually want to accomplish is already in the game, just a bit differently:

If you have a unit selected, hold down the right mouse button. You will get exactly the movement preview that you are asking for. If you think the path is fine, let the button go on the target tile. If not, hover over the unit (or an impassable terrain tile) und let the button go then. Hope that helps.

There is actually a button to use the move cursor, right next to the movement point counter.

In this cursor you will always see the path taken by the army.

On the "normal" cursor you can maintain your right click to see the path and cancel by releasing the button on your position.

Thank you!

Your information will help when I begin to play again.  :-)

I don't like how the movement in the map is simultaneous, i makes for some really annoying moments. You can get cought by the AI easily because they have lightning speed command over their units and also can make the player make a ton of mistakes thinking a unit is on a tile yet the AI decides to move as you are moving your troops in. Basically as the player the move is to wait for the AI to make its moves and then make your own but at that point it might aswell be turn based movement so... maybe make it turn based please?