Yeah I'm sure there's so many places the writers want to go with Spike but the network heads at the HUB won't approve. Judging from Daniel Ingram's panel at Trotcon 2013 there's a lot of red tape the HUB makes the pony staff go through. They're very particular about what they want put in their shows.
I've always loved that moment in the show- of Spike holding his tiny hand to the monster's print below. And you know, after watching Secret of My Excess, I was a little flustered that there were so many questions still (turns out Spike was, too, b/c his next episode was his journey of self discovery). Not so, now. I actually like how we're left with those thoughts, because Spike is, too, and all he knows is that dragons are monsters. I hope this is challenged in season 4. Sorry, great picture lol