For a coin not yet launched the initial financial risk (acquire a lot of coins of a coin with maybe no future value plus building a substantial personal network) seems like a no-go to me. What about an "established" PoS coin? Costs of the way described could be astronomical?!
You can reduce costs by trading in wait time. As long as you have some coins and sit on your wallet and stake them, as time goes by major stakers will "trip over" or get out. You can attack the coin.
Now you might think that it costs a lot to buy a whole coin. But in reality, after the top 300 altcoins, it costs less than 1000 USD to buy one completely:
http://coinmarketcap.com/4