Character 7 of 50 for the DC Core Set:
(http://orig00.deviantart.net/a473/f/2015/329/6/6/the_martian_manhunter__j_onn_j_onzz__character_by_overpower_3rd-d9hz0bl.png)
Specials:
http://overpower-3rd.deviantart.com/gallery/
i love the IA!. The fighting boost is appropriate, too. i'm not so sure about the energy boost to 5; make him a tad more expensive to use, and is unnecessary if you plan on giving him an energy boost special. (i like the notes included with each card - it gives more info on where you're coming from & going to.)
seems the Justice Leaguers are rather high cost characters (though no argument from here) - i can only assume the associated location will have a negative IA similar to Avalon from the legacy set. (time will tell...)
I had originally planned on giving him 7E, considering how versatile his powers are (invisibility, intangibility, energy blasts, and shapeshifting), but I didn't like how much I'd have to compromise his Fighting to make him fit 23 points or less. So I decided to go with 5s across the board, which lets him use up to level 5 Multis (and the 5 Multi Teamworks and Doubleshots). Because really, if anybody should be able to use those it should be J'onn.
As for the JLA Location (likely the Watchtower), it won't have a negative IA per se, just not a hugely beneficial one. A minor bonus compared to other Locations. I kind of hate the idea of negative IAs, nothing turns me off a Homebase more.