Are the coin prices automatically fed into the coin switching program? And how rapidly would they be able to sell what they mine?
I presume it all hangs on price and how quickly you can dispose of it. It's not much use if you sell once at the end of the week. Whatever spike you benefited from might have evaporated in terms of price by then.
You can't spend the reward from a mined block until 100 blocks have been mined on top of it. At 10 minute block times that means you can't spend your mined coin for 16.7 hours. Assuming you have enough hashrate to get daily pool payouts, you could certainly mine a coin and sell it the same day to lock in profits. You would have to have a lot of hashrate to make this worthwhile though.