I painted my Trukk black and gold, but the undercarriage I painted Red. (This is a Stealth-Red Job. This way I get the extra movement, but the enemy doesn't need to know that!)
I agree that Nobs for your Boyz Units are a nice idea. It is SO GOOD to get that higher Initiative for at least one of your Boyz in the unit, and the Nob can take down lots all by himself.
I like your Dread/Mek Combo. Is it worth it? I say if it makes you happy, do it. I think it is useful enough to keep. I have problems keeping a single dread alive, but I am sure the Mek helps - why not get another Oiler or two while you're at it, just to make sure?
Re: 30 point vehicles being useful... Idea for you. Ever tried Spikes and Blades? I like these on Buggies, plus a Skorcha. You have to get close to an enemy to use the Skorcha, but it is sweet! If he is still alive, he might just charge you (you want this!) and then he dies on the blades.
FOR THE FUTURE:
When you expand your army, I would get another box of Boyz and go for the max 30 in a unit. If you find the Stikkbommbas really useful, you could make a couple more of these guys as well (I think the Stikkbomba Box Set includes LOTS of extra Bombz, right?). And as already mentioned, definitely custom-build (or buy) some Nobz. If it was me, I would get some more grots also since you might want more as your army expands, but grots cost lots, so if you can't do it, maybe your Big Mek and Forcefield could pick up the slack by giving more cover to some of your boyz.
You might want a retinue for your Warboss... this is highly optional since more Boyz can work just as well often enough, but some people like to play with these guys. It also depends on how often your Boss gets into CC. A Trukk could be fun, too (I love these) because they can get the Boss (or some Trukkboyz) into battle fast. Ah, I see you are not into this, tho, so that's cool, too. In that case, more buggies are a good plan - I think you will need a little something that is fast as your army expands. What you have is good for 1 thou, but another 2 buggies maybe would help in a 1500-2000 pt force.