Frankly I would never lend my money to a bank or other party which did not pay me for it, and would never even consider paying an entity to owe me assets. I would defnitely keep my money in cash before paying someone to owe it to me, if those were the only choices. You can easily hold a million francs in 1000-franc notes in a bank safe deposit box which costs 50 francs per year (0.005% negative interest as opposed to 0.75%).
There are plenty of Swiss banks which do not charge negative interest, so why not just up an move your assets?
I find small regional banks are generally much more favorable. This likely has to do with the SNB negative interest rate exemptions for up to certain amounts of required cash reserves. My bank even pays me some interest on the balance of my private account, and relatively good interest on savings account balances.
PostFinance is kind of between a rock and a hard place because it cannot engage in many of the money-generating activities which commercial banks engage in to offset the cost of the SNB’s negative interest.
You can also keep your money at several different banks. That won’t just help you avoid negative interest, but it will also maximize the benefit of the depositor protection scheme and diversify risk.
There is also the option of holding short-term interest-bearing bonds or medium-term notes in place of part of your cash.