If the person who has the DLC hosts, all players will be able to use the DLC in that match, so generally whomever has the most should host.
In terms of the mod and if features are used, Stellar Phenomena is used for random events, Forbidden Worlds is supported in that the social/industry spec can be used in the mod (but there's nothing mod-specific that it cuts you off of) and Outlaw Sectors is irrelevant to the mod.
Depending with which of my friends I am playing Ascendancy, I had to deactivate DLCs to play and save games. Are we missing things playing without these DLC ?
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