Here's my idea for a movement preview feature which is just an extension of what @podbelski said in the second post of the thread:
Player clicks on a soldier, hovers mouse over a distant square and presses Ctrl-Shift. The UI will show the path the soldier will take to get there like it does in X1 and a little window will appear next to the target square showing all the actions that the soldier will have time for. Now if the player CLICKS on one of these actions (while still holding down ctrl+shift), then the movement preview feature will deduct the number of TU that the selected action takes. The player can then click on a second square and in so doing create a chain of actions. This could all be represented by a phantom outline of the soldier moving along the planned route.
Essentially, this is just borrowing the turn planning mechanic from Frozen Synapse, but unlike Frozen Synapse, you're never committed to keeping the full plan for the entire turn. If the soldier spots an alien while he's walking to his destination, then the player can just abandon the plan and take some other action. This is just a feature to help the player better plan his moves, and it doesn't need to be used at all if the player doesn't hold down Ctrl+Shift (and in actual fact, it would probably only be used in hairy situations and not for hurrying all your soldiers across empty ground to get the last alien).
Regardless, I think that a flexible movement preview function like this is more useful than an XCOM-style TU reserve button because the player can throw in turning, crouching, or whatever he wants, which is something you can't really do with a TU reserve button.