I suggest you to buy that wallet, they allow aproximately 20 altcoins if i am not wrong.
I have seen the Ledger Nano S, and the electrum desktop wallet etc. All nice, except I have invested in so many coins, there is none that can fit into one place.
You havent clarified if most of your altcoins are erc20 tokens, if they are, then let me tell you that you can have myetherwallet attached to your ledger nano.
Maybe this is not the best practice, but they allow you to connect it and everytime that you want to send a transaction you need to confirm it by the button, so yes, it is safe enough.
Or just buy a trezor, they have more altcoins.