Well, I tried to abuse the semirandom behaviour of the placement in The Big Push to let my squad face south and wipe out Jez's best men with a single snapshot, but I failed. All of them were placed facing north, so they have died miserably in the first round. If you want to improve the process, use my methodology. Store the squad member + direction + location information. If you undo placement and repeat placement, the same direction will be used, like now. If you place the unit to a different location, the direction will be random again. If you place, undo, place, undo, ... 10 times then you place again to the first location, the direction will be the same as it was at the first time.
Now you have 12-36% chance to have the unit facing the right direction and then 30-60% chance to hit the target with an opportunity fire. If you have 8 replacable units, the first chance goes to 64-96%. I think this 96% make people think that it is certain to place the right unit facing the right direction as they want. It is not certain, just highly probable. My solution will not decrease this chance, just make the deployment process longer and more complicated. This could be by itself enough for some people to give up on playing with the directions.
Your solution with the fixed directions increse the chance of the right direction to 100%. You might be unlucky with the unit stats, but the directions will be fixed. Just make sure you equip the right people with the right equipment. If you make the starting point random, so we don't know before deployment which unit will be facing north, you still have 100% chance to get a unit facing the right direction if they are all equipped with the same weapons.