Okay, just my $.02 here...
First, I would have to agree about the chessware...it sucks. I can play OTB and online somewhere between 1300-1400, but if I play a 1200 Chessmater 10th edition player, I get beat down like a bad habit. Crazy.
But, getting back to the real issue at hand, and tossing in my own personal experience I would have to say that a lot of the below 1200 rated players have a psychological disadvantage. I have a pretty decent understanding of endgame theory. And I can do well in the middle game. I have limited understanding of openings at all and often times Im just tossing my pieces out there hoping I dont screw up too badly. when I first started playing I would fight to the last man and hope for a stalemate when I was obviously beaten. Now I just resign. I can see forks, and sometimes traps. I think 4-5 moves ahead (although it doesnt always work out the same way OTB as it does in my head). One of the biggest things that I notice when playing lower rated players is that they not only dont see the forks coming, but they are afraid to loose pieces. Chess isnt about not loosing pieces. It's about trading pieces for position, or trading pieces for better pieces, etc. There have been many a game where, if my opponent had just called my bluff or moved his power pieces down to threaten me back or just took my queen and lost thiers instead of running away the game would have turned out far differently.
Another thing that is slightly difficult to quantify and measure, but should be tried, is that each person thinks differently. We have different analytical processes, we have different preceptions and different preconcieved ideas. Some of them cultural, others not. As a result, we will also be more inclined to develop our "area of expertise" that suits us based on a combination of all of those factors. An example, I know that I suck at attacking, so I prefer to black black. I play defensively fairly well. I play offensively rather poorly. I can see the attacks coming from my opponent and stop them a lot easier than I can plan my attacks out on the board. I win by allowing my opponents to make enough mistakes that I can exploit to beat them. With other players the opposite is true, they will just attack and attack and attack and keep the opponent on the ropes and psych them out. The psychological aspect of the game, in my opinion, has at least as much to do with rating as understanding the rules and principles and techniques.
Im also very interested in this and I'm willing to help you undertake this project in any way that I can.
I think that most players below expert level are primarily tacticians. For the most part, their rating is a reflection of their tactical skill and their board vision. Most of their victories are the result of executing winning tactics (or plundering blunders) and they often have very little positional or endgame knowledge for the simple fact that they've never needed that knowledge to be successful!
As ih8sens alluded to, tactics will only get you so far. Once these players start to face off against players who know more tricks than they do, they either get serious and dedicate themselves to further chess study or they get discouraged and figure they've reached their peak.
If you're referring to OTB ratings, this is a huge underestimation of players below Expert level. Class A players are typically competent positional and tactical players with a high degree of chess understanding.`Your generalization better fits Class C and below. Although, even Class C players understand the rudiments of positional play and don't just rely on tactics.