Funnily enough, I don't find memorising long Diceware word sequences hard at all - it's possible to construct a whacky story from them that makes it memorable. The only caveat I'd have with the suggested technique is that before you knew it, it would be programmed into a cracking tool, particularly the rhyming endings. Probably don't lose too much entropy with that though, so I think this is a basically good idea. Wouldn't trust an online tool with it though!
A little bit of math can do wonders in turning something really simple into something really long and complex. You just have to remember the seed and the formula, the math will take care of the rest.