He didn't combine all the gunpacks, he's just playing on an earlier version of the map, where all the weapons were still in. And on my stand of knowledge, there is no way of just combining all the gunpacks because the scripts of each individual pack would interfere with each other causing errors. But i can understand why u would want all of them combined. The mw19 weapons are cool and all but get boring real fast.(still very good port of them).
TLDR; Doesn't work, sorry

oh okay, thanks a lot