I was unaware that you could place a boost on your spawn turn (but now that I think about it, it makes sense that this is of course possible). So this concept is already implemented naturally in conquer mode, just not for full map, and hence it should not be a question of if it is useless or not for conquer.
I would like to see the first round of play as a round where you CAN`T attack, just place defensive boosts.
So I'm not sure why it is even discussed in regards to it's usefulness in conquer. It is useful, it just already exists, as this is exactly what the first turn in conquer is (no attack, place location and boosts).