Don't think to simple about 40 people.
I played a lot of 40 people games and its very hard but worth the ladder points if you are number one. (350 - 450 ladderpoints but you can lose 300 points to)
We had a the map hourglass and we where nod. They destroyed everything except the airstrip. And we did only defending. And we won with 5000 more points.
Same happened to me with gdi hourglass. If they destroyed you base defense. Then everyone has to stay in the base for defending and you will win.If you want to win you have to got a nice team. It's not worth that one flamer heads for the enemy base and 1 minute later another flamer etc. You have to go all at the same time and thats just the big problem.
In hourglass let in the begin know that everyone have to buy a flamer if nod and wait behind the hand of nod so that the enemy will not see all the flamers. And if you got something like 10 flames. Let 2 flames attack right 2 left and the rest from above.
But its all about teamwork yes. And know whos at the base and whos not.