So apart from all the factions within your radius and all the playable factions the folllowing are also exempt from removal because they're either racial unique to the area E.g. Bowmen of Oreon in Araby, are memorable E.g. Kislev or remain for gameplay balance E.g. Karak Azul/Red Fangs.

Full List;

--Bretonnia
"wh2_main_brt_knights_of_origo",

--Kislev
"wh_main_ksl_kislev",

--Dwarves
"wh2_main_dwf_karak_zorn",
"wh_main_dwf_kraka_drak",
"wh_main_dwf_karak_azul",

--Empire
"wh2_main_emp_sudenburg",

--Greenskins
"wh2_main_grn_blue_vipers",
"wh_main_grn_red_eye",
"wh_main_grn_red_fangs",

--TEB
"wh_main_teb_border_princes",
"wh_main_teb_estalia",
"wh_main_teb_tilea",
"wh2_main_emp_new_world_colonies",

--Dark Elves
"wh2_main_def_scourge_of_khaine",

--Wood Elves
"wh2_main_wef_bowmen_of_oreon",

--High Elves
"wh2_main_hef_saphery"
"wh2_main_hef_yvresse",

--Lizardmen
"wh2_main_lzd_itza",

--Norsca
"wh2_main_nor_skeggi",
"wh2_main_nor_aghol",
"wh_dlc08_nor_vanaheimlings",

-Skaven
"wh2_main_skv_clan_skyre",
"wh2_main_skv_clan_moulder",

--Vampire Counts
"wh_main_vmp_mousillon",