Contractors recently released a beta client that allows for custom maps, game modes and an increased player cap (up to 16) I've been meaning to try this so I'll be hosting a lobby on Wednesday at 8PM EST.
https://www.timeanddate.com/countdown/generic?iso=20200513T20&p0=179&msg=Contractors&font=cursive

If you'd like to join you'll have to download the beta client from their github https://github.com/kcmonkey1992/ContractorsModSupportPreview/releases/tag/Steam
Just download all the files with the steam prefix and extract them to one folder. From there you can just run the .exe with no problem as long as you own the base game.
When it comes to actually downloading the mods, you'll have to do that in game. It's similar to how Onward handles their mods.
Unfortunately, you can only host a lobby with a certain amount of mods loaded in based on their size, so I can only really make a lobby that has roughly 6-7 mods in it.
Make sure you have the following mods installed before joining:
-Kill confirmed and free for all game modes
-WWII loadout
-MW2 Sub Base, Wasteland and Scrapyard
-MW3 Dome

Please note that some of these mods are relatively big, they can range from 500 mb up to 1 gb. Give yourself enough time to download them before the lobby starts.
I'll see you there, operators.