I don't think I could stand to see any of the guys in here dressed in spandex screaming at me for a half hour every Sunday morning trying to sell that thing. But it's an idea.
I think that any HST oriented equipment has to have some special HST specific hook to make the machine unique. The most desirable feature I could think of is some way to make it possible for a person to do negatives without a spotter/safeties.
One idea I was toying with was the idea of magnetic resistance, used in a unique way. Make a standard pulley machine, or semistandard anyway, but instead of a weight stack the cables wrap around an axle of some sort. The axle goes through the center of one or two electric engines, and these provide the resistance, technically in the form of torque necessary to turn the axle.
Now what you do, since all the "weight" is actually electromagnetic, is put some kind of switch in line that the exerciser can either preprogram or operate manually. The switch turns the engine on and off, and so can reduce the resistance at the bottom of the range of motion so the person can move the bar back up, and then switch the engine back on and do a negative rep. So on and so forth.
It should also work pretty good because electric motors have their highest torque output at low rpms. The only problem I can see is getting the pound/feet, or foot/pounds or whatever the measurement is of torque, as consistent as possible and equating those forces with actual, physical measures of weight.
It's fairly simple, I've been thinking of ways to modify a regular universal machine so such an engine could be mounted on it. No luck, but I'm not mechanically oriented. What do you say we go in half and half on this, Bryan?