Actually, it is fairly easy with United Miles. I did something similar a couple of months ago. Since United allows a free stopover, you can have a free stop in Europe, and continue on to SE Asia. Total Mileage should be 65,000 for coach. There is an offer for 55,000 after first spend on the United Explorer Card. If you and your friends each sign up for the card, it can easily be achieved. You can get transfer from SPG to get the remaining miles to United for your friends.

Here is what I did for 65,000 miles: MCI-ORD-IST (Stopover)-SIN (Destination) BKK (Open Jaw)-LAX-IAH-MCI

Good luck.