I knew about the Jointenna, would be perfect if it didn't knock out channel 8. And I know enough not to use a backwards splitter. However I have wondered if something like this would work: The main antenna already has a preamp up close to the antenna, with power supply at the bottom. Could a second antenna also be run into an amplifier and the the output of the two amplifiers combined using a backward splitter (since both antennas are being run through a one-way amplifier, I just wonder if that would minimize any normally adverse effects).
What about if both antennas went into separate small distribution amps (say something like a couple of Channel Master CM3410's, just to pick a model out of thin air) and then the outputs of both amplifiers were immediately fed into a backward splitter using maybe 3-inch coax stubs - I don't imagine that the signals can pass backward through an amplifier, and I'd have to think that such a short length of coax from the amp outputs into the splitter would prevent multipath issues, but maybe I'm not understanding the problem fully.
I think I have said before, what's really needed (and could solve a LOT of problems) is a digital demodulator/remodulator - basically something that would take a single channel from an antenna, extract the digital stream, and remodulate it onto a different channel that could be fed into a home system (WITHOUT converting to analog). I'm sure cable companies have things like that, but even the least expensive units I've seen are running about a grand now, and I suspect someone could make a consumer-grade unit and sell it for a lot less but so far, no one has (that I'm aware of).
Actually, you know what some smart company really ought to make, now that electronics are getting so small? A multi-channel unit that could be mounted on top of a tower (like an antenna preamp) but that would convert any four channels to any other four channels before even sending them down the cable. So, for example, you could convert that somewhat weak high UHF channel down to a low VHF frequency before even sending it down the coax, reducing loss and other issues. And, if that device could also accept feeds from multiple antennas, you could do just about any combination. Remember we are talking digital streams here, heck maybe you could even send them all down the tower on weatherproof Cat 5 and then remodulate them at the bottom - lots of interesting possibilities if you really think about it!