I don’t like the reverse direction (logistically impractical) or reverse grid (potentially unfair from a sporting perspective, though I’d like to see it from an entertainment perspective) suggestions.
I think the only way you could ensure the races on the same tracks are different prospects is to run one with harder compound tyres and the other with softer compound tyres.
A slightly more controversial but similar idea would be to run the second race with a mandatory 2 (or even 3) pitstops. This would make it different, the same for everybody, but would lead to some exciting strategy discrepancies and spice it up a little.
Short of that… I wonder if Bernie has his sprinklers to hand!