That one is simple: MCO merges the lines after the ID check. Absolutely boneheaded, and the sequester is only making it worse. (I suspect that is why MCO is going for this option right now -- they are probably arguing that if the money was simply being paid to a contractor, then the contractor could keep the staffing levels up because they are not wedded to line-item values. True enough, but they also are going to want to make a profit, so it is almost surely true that a sequester would make them cut staff back in the same way if not more severely.) In practice, it is just like what happens when you close a lane on a highway; a bottleneck will develop where the lines merge ... UNLESS you have a patrolman standing there directing traffic.
My home airport does it the correct way, as does Chicago Midway: merge the lines BEFORE the ID check, or have a single line guided by ropes, then have the persons doing the ID check direct the travelers to the proper belt. A single line at ID check usually functions well if you set it up so that the ID inspectors are sitting on both sides of the line. If you put 4 people there, they can check large parties simultaneously and easily move them along. My airport has three checkers at each security area, one to handle families with children and/or disabled or elderly travelers, and two sitting about 8 feet apart who handle the rest of the line, while directing travelers in turn to the 6 scanner lines behind their podiums. It doesn't take up much space: the bin stacks are located only about 8 feet behind them, and that works because they can control the flow of people just before they approach the bin stacks.
The Black Diamond line, if there is one, should have a separate person doing ID checks, and no one should be in that line with more than one bag. In reality, if you are wearing business attire you normally can get away with getting into the BD line with two bags; because the clothing tells them that you are probably a business traveler, and therefore more likely to know what you are doing.
At both of these airports, there is an extra, out-of-the-way scanner belt that is normally used for airport employees, but there are ropes/posts set up to lead to it that allow it to be used as a temporary overflow express line for BD travelers when the lines get long. That takes the load off the main bank of scanners, and helps move the lines along more quickly.
The system WOULD work at MCO, and in fact, I can remember a time when the lines there were set up similarly. It is only in the past 5 years or so that the current bottleneck has developed at the A line.