S - Observant
A - Adrenal gland, Modified reserve, Fearless, Down range, (medic with berserker/Samarai)
B - protection, energy cell, medic, cooling syncs, big pouch
C - impatient, long leap, dithered lens, heated, light bender, trapper, inpenetratable
D - height advantage, branch master, spectral awareness, hanging on, ascender, fast hands, clotted
F - resourceful (you’ll gain more xp by picking a useful perk and performing better)
My picks. I tried to take into account opportunity cost.
Medic is a little different, because it helps you heal faster from second wind, which makes it a good pick for the Berserker or samurai. Observant not only mitigates muddying up, but it allows you to track the movement of multiple fireteam players at the same time. Protection will keep your mask on, even if there is an annoying sawz50 on the other team.