I think I'd try to get extreme customer loyalty by making it much easier to use miles. I'd make more seats available, in coach at least. When current events drastically reduce load factors, I'd offer big mileage sales (15,000 RT to Mexico right now, for instance. Weekend specials would also have weekend special FF rates. Hopefully, making miles easy to use would attract a lot of customers and keep them. I'd allow one-way trips, open jaws, layovers, and multiple destinations.

I would offer fewer bonus mile programs, unless they were with a partner that was paying me a lot for the miles and the advertising.

Hopefully, miles that are actually useful would attract and keep customers, especially business customers.