I've done some checking and researching, and from what I gather the only thing Roblox has on us is dynamic brick shaping and brick-based vehicles. I'm not sure if Blockland can reshape bricks that easily, but maybe we can do the other trick...
They seem to be able to make vehicles out of bricks, on the fly as they play. We need a vehicle spawn brick, and an appropriate add-on to get a given vehicle. If you can mod yourself, great, otherwise you'll have to wait and see what gets made. Granted, brick vehicles don't look as cool as well-made modded vehicles, but you can just make them anywhere.
So this is my suggestion: Can we make a system to build vehicles on the fly? There are a number of ways to do this. The failling Lego Creator back in the day had pieces you could stick on a pile of bricks to turn them into a vehicle. Can we do that? I think maybe not. It seems Blockland considers blocks a scenery kind of thing that can't be moved about. But what if we built with special bricks? We have anti-portal bricks, can we do something to make moving bricks that can be stuck together to make a vehicle? Or maybe a special vehicle spawn that can make models on the fly out of user-chosen brick look-a-likes? Then you could have a saving system for the models, and can make anything you like. They would be made out segments that use the brick models, but would be combined into a single model that would be equiped with a chosen, customizable vehicle script.
Any other ideas?