This. Test it out, you don't even need access to armor. Wrist and ankle weights, perhaps a weight vest as well. As others have said, its not that you can't be as fast, its that you take longer to get to speed, and can't maintain it for as long.
As for the issue of MOV in the game, the people that I've always gamed with have considered this not so much "how fast can you move?", but more "how fast can you move and maintain situational awareness. To that, and with what Womble said above, there should probably be a DEX (or Strike Rank) penalty and fatigue component to armor wear. The fatigue component wouldn't have to be anywhere as fiddly as RQ3, just something simple as a roll of some type after exertion, as determined by the GM.
SDLeary