Yeah - it's hard to come up with a design for something that can take up the range of slack dictated by the extremes in cog ratio that ends up being more elegant than the existing design.

But once you're given an existing chain tensioner design, the parallelogram addition to move the chain from cog to cog starts to look ingenious.

Edit: I welcome someone throwing out the existing design and trying to come up with something better, though.....just don't think it's going to be easy.