Super Smash Bros. Trilogy/LBT crossover, eh? Well, I have some suggestions for playable LBT characters.
Petrie- Lightest character, but has most jumping power because of his flying like Kirby. Fast aerial attacks and staying out of range between attacks are his specialty. Lowest power and fast speed.
Ducky- Second lightest and jumping skills. Dodging blows and hit and run attacks are her specialty like Jigglypuff. Second lowest power and fast speed.
Spike- (He is smaller than Littlefoot and seems heavier than Cera) Second heaviest character. Lowest jumping skills. Powerful moves that can, but had better be for your sake, evaded. He is like Bowser and Ganondorf is his fighting style. Slow speed.
Chomper- Third lightest character with middle jumping skill. (His style of fighting is based off his hyperactive moment shown in The Cave of Many Voices when he destroys the stone teeth.) Barrages of physical attacks that keep coming and so are hard to evade like Lucario is his specialty. Slow speed.
Ruby- Middle weighted character and third highest jumping skills. Fast attacks with good strength behind them and moving around easily makes her well balanced like Mario. Fast speed.
Cera- Third heaviest character with third lowest jumping ability. Attacks with a single focus that are poweful yet harder to control like Donkey Kong is her fighting style. Medium speed.
Littlefoot- Heaviest character and second lowest jumping capabilities. Slower, stronger moves that can be hard to predict because he has a tail and can attack from both sides. Not-too-low speed with pretty strong attacks that can be difficult to foresee makes him like Wario. Medium speed.
Just some thoughts on the gang of seven. Not sure how useful this is, but I wanted to add what I could. Later!