Alright you have to understand guys the Mark V or the "Suitcase Suit" is an emergency suit. Remember it takes a team of bots to get him in and out of the suit which is the basic premise in the Ultimates books. Again the thought was that when Tony Stark is out and about away from Malibu, he is vulnerable and probably going to be attacked more than a villain waiting for him to head home and then suit up. In the latest Iron Man comics he has his "car" shipped around with him in his private plane, boarded up for no one to open except him to have his suit at close range as well as the bots needed.
Look at the Mark IV and Mark VI, they are full on Iron Man plated suits. Looks at the Mark V, its completely plated, even the helm and its very thin, close to his chest. Its a "Holy ____ they are coming after me suit" not a full on battle suit. I also love that they showed him playing around with intensity projections in his workshop which shows that the progression of the suits isn't just "we need to sell more toys" but in actuality as least as far as the film is concerned Tony continuing to refine WHICH IS COMIC ACCURATE, remember in the books Tony has over 47 Marks and some with 6 phases between them simply because he was trying to make his tech better.
It isn't about suspension of belief because it'd be less believable to have a full on suit in a suitcase OR to have him walk around completely unarmed while away from home.
BRING. IT. ON.