This is nothing just a list of top 15 altcoins after BTC which you have decided to buy. I think this might be a right strategy but in longer term only those coins will prosper who will actually make the lives of people easier or atleast try to make the lives of the people easier.
If you choose 15 alts, it is better to choose them from the top 100 markets, because if you look for coins that are in the middle of the market, you can get to the scam
Yes I agree but it's not that the top 15 coins today will always remain top 15 coin so OP is correct in accumulating different rank coins.