i dont think there is a native way, but i have wondered about this before too. ill post a few ideas, although my biggest hope lies within method 2. ( that there might be an addional download-creating-able sidemodule that isnt used by the map, but can be used by the server - map unrelated downloads)
1) steamworkshops sv_broadcast_ugc module supports an overwrite functions for specified maps.(updates) maybe hack into the download function of this module and create artifical downloads? the module supports http requests thus -> method 3
2) is there a side download module, running on the server? (demo file download communication, comes to my mind )
3) is there a way to directly push http-requests from the server to a client? what about sending an external http request? ( maybe even use calls of
https://developer.valvesoftware.com/wik ... r_protocol)
the next will definately work,but requires additional work and would be sp unrelated:
4) create your own client, create a pipe, and manage(replace) files/downloads manually.