I totally get what you're saying about "powering up". Investing steem into steem power and holding it for a while makes perfect sense. But with Steem Dollars consistently worth more than Steem (and even when not, since you get more value in the 50/50 reward from the Steem Dollars), I've found it's much more advantageous to keep the posts at 50/50, and then sell the Steem Dollars on the internal market for Steem. And use those to power up.
See what I'm saying?