If you automate the rewards, such that we only reward people for preparing and expanding profitable systems, then you cannot attack by contesting systems, and you cannot bring systems into the exploited bubble for reasons OTHER than CC. For example, Mahon gets trade dividends. Suppose we found a trade route that would give us 4,000 credits/ton each way, but they are the only two systems in that entire bubble. That'd be a massively unprofitable system in terms of CC, but the 800 credits/ton extra we could get for grabbing it would be well worth it. Under your rules, it becomes prohibitively expensive or even impossible to try to grab that control bubble.
Similarly, if a player group comes to us and asks us to protect them from a Federation power's incursion into their space by exploiting them, that also becomes prohibitively expensive or even impossible to try to help them out.
Or suppose that we're in an economical war with the Federation (which we are), and we notice that there's a particularly good set of systems that they could expand into (but haven't yet), but are loss makers for us. Currently we could choose to expand into them to deny the income to the Feds, but again under your rules, this is not allowed, because it's not profitable.
This is why it is a strength that we are allowed to do things that doesn't make sense in the purest terms of PowerPlay. There are lots of reasons that CC profit is not the end all and be all of PowerPlay expansions, and these are but a few.