Um ... how far to take it really depends on what look you want to achieve. Personally, I think they look great as they are, but here's some ideas:
Add lighter coloured dust to the wheels and the upper surfaces. There's a few techniques you can use for this but the main ones are filters and pastels / weathering powders. The dust on top would be lighter than the dust near the ground, partly because it's thinner and partly to simulate strong top lighting. As these are presumably in service in Iraq, the tyres might benefit from some dustiness.
Dry-brush. I know it's old hat now but I still find that dry-brushing helps to bring out fine raised detail - and on the Stryker series, the surface is
covered in little knobbly bits that love that sort of treatment. You don't need to go mad with light dust colours - that's a little unrealistic - but lighter shades of the basic colours can work wonders.
The mine plough: the main weathering here will be exposing the metal under the paint. There are two methods, depending how worn you want it. For light wear, you could go for chipping: start with a lighter shade of base colour in small patches along edges, then add smaller patches of something dark like deep brown (but not black) within them. Result - the effect that paint has worn away to the undercoat, and then in places to the bare metal. A quick rub of a soft pencil along the edges adds that final metallic sheen. For heavier wear, the method I use is to dry-brush metallic colours in layers, starting with something dark like gunmetal and ending with very light touches of silver. I live next-door to a quarry and, while it may sound as this will make the plough too bright and shiny, trust me, dozer blades really do end up like that. You may want to check what materials the plough is made from, though. If it's aluminium, you won't want to start too dark, as that gives more of a steel effect.
A few thoughts, anyway. Oh, and good luck getting past that bar armour ...!