Sadly not possible currently I believe, as it is tied to Steam Workshop integration. Previously one could export the Workshop content and get it somewhat to work, but that opened up a can of worms of issues (one is distribution of a multi-gb-sized mod) as well that it will interfere with multiplayer as it would have to be exported into the main folder of Wreckfest as opposed to the mod folder that the Steam version uses.
Sorry for being bearer of bad news.