Bill, with much respect...I've owned many cabs that were made as well as anything out there...Epifani, Bergantino, Genz, Schroeder...and much prefer the sound I get out of the MB212..."for my sound". Maybe I 'like' the peaks and valleys created by 'wrong' cabs?
Depending on what and where those peakes and valleys are, they may inadvertantley suit the sound you're looking for right now. Don't forget, "if it sounds good, it is good". That doesn't take away from the fact that it may actually sound better or by making it better you can make it to sound "better".
The MB210 may indeed be a little "gem" here where the speakers, the box and the amp (or not), despite the short-comings of each may enhance each other and turn out to be a good combination but simple, time-proven concepts like making a solid box and using decent damping could make it that much better for what?
As rspands estimates...$5 in material and a hour or two of your time? That's retail....When you as a company makes these things by the hundreds or thousands and factor in wholesale prices you're talking what $1.50 per cab? Put a 300% markup on that and you're still under $5...that's lame.
I made page 13 on how to make a cheap cab better. Like it or not, this is one of my fortes. Now before we go on about 1/2" birch and driver alignment, let's remember this is supposed to be a very cheap but good sounding cab. This is why pieces for the combohead mount are included in the cab version that doesn't have an amp in it. It's cheaper to make a lot of one thing than it is to make 2 different versions of the same thing. Labor and re-tooling are more expensive than material. 
