If you have a radar it does have an arrow though, right? So a better solution would be to add radars for any maps missing them. That would require a server plugin to have clients download radars, but that beats editing maps to add radars or removing the ability to use cardinal directions.
I loaded each map in the map list and this is what I came up with:
Has radar packed in
ba_mlcastle_se
jb_avalanche_csgo_b7
jb_coldcampus_pg
jb_minecraft_beta_pg
jb_obama_v5_beta
jb_peanut_pgfix
jb_sand_pg1
jb_spy_vs_spy_pg_v4
jb_umbrella_pg_fix
jb_undertale_v1c
jb_vipinthemix_pg
Does not have radar packed in
jb_august_2k17_v1b
jb_cavern_pg
jb_clouds_pg
jb_jailberd_pg
jb_k1ngphoenix_b1
jb_longstreet
jb_mist_v1_pg
jb_paradise_winter
jb_parabellum_v2c
jb_pleaseworkv420_pgfix
jb_quake_a03
jb_renegade_pg_final
jb_seascape_beta2
jb_sg_dojo_v4-1
jb_vice_pg
Radars for most of the maps in the second list exist already, and it's a
5 minute process to create a simple one for those that do not exist.