You can hold, but I suggest that you don't hold the full amount in BTC.
You can consider to use part of the fund to buy some very popular alt coins, such as LTC or DOGE, when their prices are low.
So you will be able to migrate some risks, and not solely be affected by BTC price fluctuations.
Or he can invest his 12btc in ICO project, usualy some altcoins are get famouse then the price is rise until more than 250% when the coin get in the exchange site.
I think the word "usually" is an overstatement. There's just far too much ICO project that go to waste to use the "usually" word. If anything, ICOs "usually" are just something that "devs" are using to make quick money.
Back then, there might be coins that reach that 250% but today? I don't see that much coins rising. There are even coins like vDice that are already in the exchange site before they released the ICO bounties and it's already been dumped. Up to now, VSL (vSlice or vDice coin) hasn't got past to their ICO price. There has been 2 or 3 times that it got past 10k but since there's too much people that holds VSL, it goes back to 5k price after a day or two.
We do not easy to trust any project ico coin if they are do not use escrow for ico fund. Because at least if there's a escrow our money is safe enough. Not every ico of alternative coin done successfully sometimes the ico fail and finish with that alternative coin dump in unpopular exchanger, it is so terrible.