Really you want to keep a good portion of your portfolio in Bitcoin. To get the best of both worlds you could easily sell part of your portfolio at a loss for some BTC and hold both.
Alt coins should have a strong connection between BTC since people most of the time go FIAT -> BTC/ETH/USDT -> Alts. Bitcoin is always used to buy alts so the price of alts is pretty much always in satoshis and not fiat.