As a matter of fact, I believe that the LIGHT tracked vehicle you mention already exists, and has been around for many years: the M-113. Easily carried by a C-130, and there is a huge vareity of add-on armour kits for it, ALREADY IN EXISTENCE. And they are almost as cheap per copy as a HUMVEE, and a LOT less expensive than a Stryker.
Yes, even I'd prefer an M-113 with extra armour to a HUMVEE.
But please don't think that I'm advocating that the army have NOTHING but HUMVEE's for vehicles. Basically, I'm thinking of a few brigages equipped with such, and no more. And they wouldn't be used to thwart an armored advance of T-80's and BMP's, but be put into those areas of the world where there are low-intensity conflicts where the "enemy" has little, if any armor assets. Also the HUMVEE squads would be handy for those sort of tasks where armor isn't really needed, but firepower and speed are.
I've played many, many wargames using a wide variety of armor, and one truth becomes self-evident: there is no such thing as a tank with armour too think and a gun too big.