Also, personally, I wouldn't feel safe having a large amount of coins in an unencrypted wallet. I would just connect a clean computer to the internet for a minute to encrypt the wallet. If someone ever accidentally gets the same private key somehow, it is still safe.
No, it is not. You obviously do not properly understand how the system works. If someone ever gets your private key, your coins are gone. No matter how many times you've encrypted it, nor how many hardware/software wallets you've used. The encryption (within Core) of a wallet (e.g. wallet.dat) prevents people from sending money from your addresses that are contained in it. If you use a external encryption (outside of the software) it still only prevents access to the file.
However, if someone has your private key, they simply run Core and enter: importprivkey thePrivateKey "TheLabel". The person can then spend whatever was on the address.
Though there has been some news about the possibility of hackers installing a backdoor in the cold storage system, the method of securing a cryptocurrency with a cold storage is still by and large the best. Web based wallets are most prone to attacks by hackers and when the web links are snipped, cold storage becomes a safe place for the cryptocurrency you own.