I've just been reading through this thread, and it's stirred up something in me. It's challenged my fanfic, my view of LBT, and even my writing skills. I've really begun reconsidering things because of it.
I completely get the "pure LBT" view, and it does seem like it would take a lot more creativity/repression of wild ideas to write something like that. To be honest, I don't even know why I decided to write my fic in the first place.
Maybe it's because sci-fi is so easy to work with. In a sci-fi story, virtually anything can happen, and all you need is a psuedo-scientific explanation to make it sound good. Take an idea I once had of a Star Trek Voyager/LBT crossover.
It's staged during Voyager's sixth season, and Voyager's crew has a new plan for getting home. By momentarily slipping into a transwarp conduit run by the cybernetic race known as the Borg and latching onto a passing Borg vessel with a modified tractor beam, they would be able to potentially hitch a ride across the galaxy. All they'd have to do is catch a Borg ship going in the direction of Earth and they'd be home free. Of course they try this plan, and the ship they latch on to just happens to have the Borg Queen aboard. Naturally, she tries to shake them off, but somehow they manage to resist her efforts. As a last-ditch manuever she sends the ship into a temporal vortex (basically a time travel thing that the Borg have been known to create), and both ships are hurtled back in time. Suddenly, they both drop out of transwarp. The Borg ship has broken apart due to the stress of reentry on its hull, but Voyager's tougher superstructure is able to withstand it. The Borg fall into the gravity well of a nearby planet and break up in the atmosphere. THe crew of Voyager realize that the planet is Earth, but they soon realize that they went farther back in time than they thought-about 65 million years farther. They decided to beam down to Earth and see if they can recover any bit of Borg technology that might help them return to their own time. Upon beaming down, however, they find themselves surrounded by five young dinosaurs.
See what I mean? It took me five minutes to think that up. Sci-Fi is immensely easy to work with because it has no bounds. I'm not saying it's good or bad, but that might be the reason why it's so popular.
Another point mentioned is the fact that most crossovers do not blend the fandoms equally. This certainly applies to my fic, and it's only going to get worse. Right now, the ratio of LBT content to Star Wars content is about 1:2, and, if I follow my vision for the story, it's only going to get more Star Wars-y. It's just that the Star Wars universe is so much more vast than the LBT universe, and I see so much more possibilities with it. I wish I could keep it more LBT, but I feel as though the LBT characters, over the course of my story, sort of undergo a transfer. The line between the LBT and Star Wars universes is removed, and each mixes with the other.
The songs are also an interesting note. While I agree that having the LBT characters sing modern songs is more than a bit strange, I think that LBT songs are written specifically for the situation in which they are sung, and most people simply can't write their own songs. Including modern songs seems to be the next best thing.
I know this is getting really long, but I just have to get this down before I forget!
The sharpteeth armies are a particular point of contention as well. While I agree that sharpteeth would probably never form "armies", but it seems to me that the predators livng in the lands around the Great Valley might not be getting enough prey, due to the fact that all the herbivorious dinosaurs live in the Great Valley. Perhaps the smarter predators, like raptors, would come to the realization that, in order to surivive, they would need to enter the GV and remain long enough to eat their kills. This would require subduing most of the defenders of the Valley, i.e. Mr. Threehorn or Grandpa Longneck. To do this, they would need many of their own kind to attack at the same time. Then, if the packs of raptors outside were able to enter at about the same time and attack, the wave of raptors entering the GV might seem something like an army from the plant-eaters perspectives. Again, this is still a huge strech.
So what does this mean? Because I combine LBT with Sci-fi or other elements not seen in LBT, am I less creative? Is my writing worse than I thought? I didn't think so at first, but the more I think about it the more I question myself.