It would be a real challenge to make Invasion of Tinysauruses a good film. The overall plot idea is just bad. However, making the Tinysauruses less annoying would be a good start. Big Daddy sounds and acts like a bad Pixar character (I don't like Pixar as I've mentioned earlier.) They are just one deviancy from the overall tone of LBT and making them more believable would be essential to improving the film. Also, I just hate Tria and this film because it introduced her into the series. Just cut her off.
The other plot point, Littlefoot's mistakes, wasn't handled maturely enough. His eventual confession was good enough but the scene with the Gang was very lackluster. Why did they have to handle it with mere sulking and a cartoony cry? Not like this. Also, the two first songs are terrible while If Only is just meh. The best case scenario I can see for this film is that the tinysauruses would have been neutral, frightened characters and there should have been more scenes of the Gang's internal struggles.
I don't have too much against the 12th film. Guido is one of my favorite guest characters and his personality was more interesting than many others'. However, I found parts of the film somewhat slow so there could have perhaps been some struggles with Guido's past, an old rival/enemy or something. There just wasn't too much going on. His sleepwalking scene took a good chunk of the film so it should have had more impact. And once again, cut Tria and Tricia.
The Great Day of the Fliers was a decent idea but there should have been more actual challenge in it. Right now, it was just that Petrie wan't able to fly in line. :huh: There could have been more difficult tricks, more training or something that could have kept the show going on.
Surprisingly, I find only one element truly wrong with the Wisdom of Friends: the cursed Yellowbellies. The thing with the Wisdoms wasn't too clever but I didn't mind it. The plot of helping a group of dinosaurs find their home was okay (completely different from the ninth film

) and the environments were satisfactory. Had the guest characters been better (as good as Guido or Shorty), the film could have been a solid retelling of the Journey to Big Water. The theme of questioning the conventional knowledge is alright and as I said, the look of the film was okay. But for goodness' sake, improve the animation!
I still like JOTB even if a lot of potential was lost. Making it really good would as simple as exchanging Wild Arms to Shorty and giving more time to Bron. This way the story would have had far more depth than any of the past sequels but Doi apparently wished to throw it out of the window for no reason. Ruby and Chomper should have been given more time, too. Even if it would have been nice to see more of them, I guess they're lucky to have been excluded from the 13th film. Also, cut the lizards, seriously what? I've skipped that scene ever since my first viewing.
I hope I managed to sort out some easy improvements for those films. These alone wouldn't make the films great but at least much more satisfactory.