Help Choosing AW Defenders

DoctorofEvil

Five Star: Ultron
Four Star Duped: Medusa (Sig 39), Void (sig 49), Abomination (Sig 20)
Four Star Unduped: BP CW, Dorm, SM MM, AV, Hulk, Cable, Kingpin, Punisher 99, Nightcrawler, Green Goblin, Morningstar, Quake

Some of these are not ranked up at all, so I want to pick 5 and upgrade them specifically.

Primmer79

The great (/s) thing about this game is that as soon as you rank up a 4*, you'll get a better 4*. or more 5*.

From what you have, I can give a few suggestions, but you have options.

5* Ultron - useful beyond AW Def.
4* duped Medusa and Void - Elite defenders, albeit 4*, and useful beyond AWD.
4* unduped:
NC- If your alliance ends up going for diversity, theres always 4-5 NC that just sit on the bench in the BG, so meh, good for defense, but be prepared not to use him. But he is better for defense when unduped.
BPCW - strictly for AWD, and doesn't need to be duped.
Cable - I don't use mine, and Ive seen mixed reviews about him on offense, but hes a good counter to blade on defense.
Quake - Doesn't need to be duped to be used to her full potential. Average defender, Good for offense.
Punisher 2099 - Annoying specials and a different champion for defense.

MS is an honorable mention for AWD once you dupe her, Ive heard good things about her for offense even unduped.

Edit: To be more direct, I wouldn't rank specifically for defense because your defense will change when you get more champs. I would focus on ranking Void, Medusa, and Ultron, and once you're done there, see if you get any new champions.