Why keep a local copy of the blockchain if you're not mining? There's no good reason to, just like there's no good reason to avoid using alternative wallets. If you can't be bothered to spend a few minutes researching alternative wallets, just run it offline on a bootable OS like Tails. You don't need to "spend countless hours" researching and verifying whether running MEW or some other offline client is secure.
RE: Cheap and effective way to store your wallet data (BTC, ETH, LTC etc)