Sorry I was just thinking loud. For example: you want POW(no POS, Masternodes...) blockchain with 10min block spacing. This is done so far by looking back to previous x blocks solved at time y, and calculated next block diff(depends on implementation). You made first step in diff retarget intra block. But why to waste electricity between blocks. you can set the diff between blocks to diff, which is way higher than current diff of BTC and after 10min or 9,(xx/sec/)(which is your target) you can drop it to lets say "gpu solvable levels", so the block will be lottery. Doesn't matter if you have 100PH or 100GH. Of course everyone will be mining other coins between your blocks. But you will have still same blocktime and emission of coins like before. Next thing is economy, all the pow coins are valued by electricity spent on mining(so basically if you didn't waste a lot of electricity minnig some POW coin its not valuable). In my opinion, I rather prefer to mine some lottery block, if I'm not whale or don't have enough money to invest into some ICO, IEO..., or I cant mine high hashrate project. Imagine mining every 10 min xy miners with GPU's.