I don't think if it's good to buy altcoins if you just short trade only we don't know if it will decrease more, but for long term I guess this is the right time to buy and hold until the price will recover.
It's better to have a plan for the long term at this moment because, in the short term, the market will not increase so high. If he wants, he can buy an altcoin because the altcoin now is down, and some of the altcoins will be the potential to grow in the future. Holding the altcoin will have a risk, but don't worry because the altcoin will increase after bitcoin can stay at a price.
Perhaps, he needs to analyze one by one of the altcoin so he can find out which altcoin that can give him the profit. But as long as he buys the altcoin from the top ten list, I think he will make a profit later.