I'm not sure if anyone's suggested this before 'cause Iunno what keywords it'd go for in search or just manually looking back through the previous pages. Hell, it might be a feature already in Soldat that I don't know about. So... here goes. Quite a simple suggestion, actually: allow modders to specify a folder on their harddrive to take custom mod graphics/weapon settings from when hosting a server (or none at all), then add a checkbox to set the server to force all players to download and view the custom graphics and sounds during the game. Perhaps packed in like a custom map download.
Of course, this would probably be abused with ear-splitting weapon sounds and incredibly tacky colors, but that's why there could be a new column in the server browser with just a Yes/No that says whether the server's running a graphics mod.