For anyone who wants to remove specific variants, it's data\world\factions\default_ship_roles.csv you want to modify. Delete any entries that reference the BV variant you don't want and it won't spawn. Make sure you're not preventing a hull from spawning entirely though - for example, I deleted all references to modded Brilliant variants, but there's also a reference to the vanilla brilliant_Standard variant that sets its spawn chance to '0'. I don't think Brilliants would spawn at all without deleting that last entry, although I could be wrong.
It's probably not necessary but I also deleted the variant files themselves in data\variants. There are remaining references to these deleted variant files in data\variants_lib\variant_tags.csv, but the game loads without deleting those references, so the only file you should need to open is default_ship_roles.csv. Hopefully this helps someone else in the future. Thanks iBABM for updating the mod!
