That horse mask she's using in-game might also be a reference to Hotline Miami, don't you think ? Don't know much about payday, so not sure if that's something you can actually have there.
There's also a whole set of Hotline Miami masks because of the crossover DLC which added Jacket as a playable character with his own perk and skill tree. This is the same game in which John Wick became a playable character with his own perk and skill tree in a free update, plus a Goat Simulator heist DLC, so you tell me what's possible.
And yes that is a Borderlands Loader Bot snuck in there.