I like your plan overall, but personally I would consider ensuring that each state has at least one major urban centre to act as a source of revenue and influence to support the rest of the state more independently of the federal government. So this would probably look more like the 12 states you had at the start of your article, perhaps with London remaining broken down a bit more.

Otherwise you will probably end up with rural states that are highly dependent on federal support and therefore have less autonomy and more limited opportunities. The American analogies you give are good ones, but the problems aren’t only due to disparities in population counts. With purely urban and purely rural states, I believe you’ll eventually end up with an accelerated version of what’s happening at the moment; a brain and youth drain from the rural areas to the urban ones, which will in turn bring back some of the disparities we have currently – where large sections of the younger population end up concentrated in fewer states, diluting their voting power. This could perhaps be rectified by pairing up each urban area with a rural one, and leaving the different administrative approaches that are needed to the local government level.