That’s not how it works. At all.
A server is a physical object with a finite amount of space on it. A layer is a software solution for dividing the space available. Software cannot add more capacity. Only hardware can do that.
You’re basically claiming you can download more hard drive space. You can’t. Layering is like partitioning a hard drive. It might show up as a second drive, but the total storage volume is the same.
I’ll give you an example with made-up numbers.
Let’s say a server holds 10,000 people. 10,000 people all logging into Northshire and competing for wolves would be unplayable.
Layers split that server up. If they make 10 layers, then they put 1,000 people in each one. 1,000 people is far less terrible. The server is the same size, but you will only interact with 1/10th of the population during your play session.
Later on, the layers will be disabled as people spread out. If they go down to 5 layers, then each one has 2,000 people, but the server still has 10,000 players.
If Blizzard decided 1,000 people was unplayable, they could double the number of layers. That would mean you only interact with 500 people, but the total server population is still 10,000.
Layers make a larger server reasonable and playable, not possible.
I hope that clears things up for you.