Option 4 is clearly a good one, more companies should pay dividends to employees in addition to (or instead of) shareholders. Employees have a stake in the company and the usual way of doing this (by giving employees stock so that they get the same benefits as shareholders do) doesn't align risks well. These are called bonuses, and yeah, big companies should pay more bonuses when they are performing well. I'm all for any company that does that and any policy that incentivizes it.
But I'm a lot less convinced by your other two points.
I'm sure the airlines did keep enough cash for an emergency fund, but every emergency fund comes with a model of what an emergency looks like, and for airlines what makes sense to cover is things like oil price increases or a recession that impacts demand for travel by a few percent, not an event like this that results in a 95% decline in demand due to government mandates; we don't want every large corporation hoarding a hundred billion dollars in cash, we want that cash available to invest elsewhere.
And I don't really want corporations to be major leaders of philanthropic activities. Why them? Who are they accountable to? Why should I expect them to support good causes? I would rather see that money in the pockets of individuals who can decide what philanthropy to support, or in the pockets of a government whose philanthropy is accountable to voters.
The (flawed, but not entirely) idea of buybacks and dividends is that they also achieve the function of getting cash out of the hands of big corporation managers. When that cash ends up just sitting in another bank account of a rich person (or in a yacht) that is a shame, but it is its own problem for which there should be different solutions, but when that cash ends up flowing into other investments, that is much better than it sitting in the bank account of an already-huge corporation or being funneled into doomed business lines outside that company's area of expertise.