I've always wanted these things for Blockland. My suggestions:
1. T-Rex is slow, and to injure players, it chomps people and/or swings its tail (if not then just make the tail swinging its walk animation)
2. Ptrerodactyl flies at a fairly high height, and swoops down to hurt players, then circles above the player like a hawk until it attacks again.
3. Add a stegosaurus and triceretops, like in the Lego Adventure Series.
4. Add those Lego snakes that move around on the ground and hurt you.
I realize some of this would be really hard to do, especially the pterodactyl's "battle strategy". So tell me if this is possible or impossible. If you don't know, ask Rky. He's the one that's probably going to be helping you with the bot's movement.