This mod allows squad sizes of upto 20 in multiplayer! Now you can have hordes of cheap ADVENT! I may increase the max squad size in later versions. I've tested the mod on all map types in LAN and it works. It should work online as well. 

List of changes: 
The Lobby and offline Squad editor menus now allow selection of more than 6 soldiers 
The spawn area has been increased to allow extra troops to spawn 

If you can think of any improvements, let me know. 

UPDATE - I've fixed an issue that was causing the mod not to work in some cases.

Installation

1. Copy the extracted folder to this location:
 Steam\steamapps\common\XCOM 2\XComGame\Mods
2. Enable  'MPLargerSquads' in the mod launcher
3. Play