I think it's a good idea. There's not alot of actions in the game that gives you bragging rights.
There's 4 million planets in the game, and currently only probably 1/4 is worth colonizing because it would take forever or cost a fortune to improve them.
Improving a random stat by 1 (including size) for a crappy planet to have been scanned and then purged would help make the game a little easiler in the long run esp for low ranked ppl that can't conquer or hold really good planets from higher ranks that want them.
It would be hard to abuse this since the odds of scanning the same planet twice are about 4,000,056 to 1, worse than that if Dan adds more planets

The payoff would be noobs less likey to quit over never seeming to get a break on planets plus alot of longterm players having something else to do. Currently when you purge a planet the game acts like you never scanned it. Would be nice to see a new catagory for it. Total Planets Scanned, Total Planets Purged, Current Planets Scanned, Current Planets Owned, ect.
+1