If you are flooding the pieces of styrene with MEK, it should be no surprise that you have warping problems. A similar problem would occur if you were building out of wood or card stock and soaked the pieces in water first. A lot of folks use MEK as a bonding agent, but I prefer Ambroid Pro-Weld, which is primarily methylene chloride, because it flashes off very quickly in the open air, which seems to cause fewer problems. It is so fast that brush application is almost impossible, because it evaporates so quickly it will mostly be gone from the brush before the brush reaches the model. Usually it is best applied with a soft polyethylene squeeze bottle that has a superfine hypodermic needle attached. If the needle is too big, try inserting a piece of monofiliment fishing line into the needle to reduce the flow. You will also need a piece if the finest stainless steel leader wire you can find that will fit inside the needle to clean it, because eventually the needle will clog up. These used to be sold by a company called Gaunt < http://www.gauntindustries.com/1-1_4_Ounce_CLEAR_Bottle-HYPO-160.html
>. You could also use a syringe, but in a very short time the solvent causes the rubber stopper to swell up, locking it place inside the syringe body.
The secret to a successful styrene model is applying the glue in Goldilocks proportions (not too little, not too much, but just right), as well as using the thickest sheets you can, as long as their thickness can't be seen. If you try to use scale thicknesses, it won't be durable enough to survive the construction process. A lot of traction modelers build their models out of laminated paper or card stock, even in "O" scale, and some of those models look as good as (or better than) commercially built brass models. I used to use manila file folders for this, and sometimes rubber cement for laminating larger pieces. With rubber cement however, initial alignment is critical, since once the two pieces touch, they can't be moved or slid into final location.
Cutting the material and punching rivets will be tedious no matter what the material. There have been some comments made on other groups about using computer driven cutting machines for this (think of a laser cutter or printer with a different head containing a scalpel blade). These are frequently sold in craft stores that sell scrapbooking supplies, and cost just a few hundred dollars, instead of the thousands for a laser cutter. I've never seen anything actually built using this process, but it sounds intriguing.
Good luck and keep trying...
Bill in FtL