I agree the toy box mode sounds potentially interesting for people that are into that sort of thing. Same with Little Big Planet, brilliant concept, but I couldn't care less.
What really irks me about it is the business model. I don't really know anything about Skylanders so I don't know if this is true with that, but the whole notion that the models and dock thing even exist seem entirely superfluous to the game. Fair enough if you want to make accessories and sell them to increase your business, but at least have a reason for them.
And the idea of having to buy those modifier things blind is just vile.