It is an option, you just need to do the intros correctly...
You shouldn't just put a glider into another gliders cage. They can be very territorial.
You've already done the pouch swapping so you should be good on that. When you want to do the actual intro, you should do them in the morning when they are tired and do them one on one. Take your lone girl and ONE of the others and place them at opposite ends of the bathtub and let them come together as they see fit. More often then not they will sniff, groom, follow eachother, get acquainted.... if they do that, I wait about 5 minutes or so then toss them a clean, neutral pouch. Odds are they will climb in and snuggle.
I keep them on me for the day to make sure no one fights.
In the evening I return them to their own cages. The next morning I do the same thing, introducing the lone glider to another of your girls...repeat.
On the next day I would intro. the last of the 3 to the lone girl...if they get along I would add another, then another until they are all four in the tub getting acquainted.... toss a clean pouch and let them snuggle for the day. I'd either return them to their own cages that night or if you feel they will be alright, you can spend the day cleaning the cage they will share...I powerwash mine and deck it out with all clean fleece and toys. I place them in the cage IN THE POUCH THEY ARE SLEEPING IN before they wake up so when they do, they can begin exploring THEIR new environment.
I've done this will all 7 of mine and they are all together so it's been successful for me. Good Luck!