I think if you were to do timed rankings, it'd be best to do them for a week for something quest-based (timer). It's nice to be able to take a somewhat relaxed approach to it, instead of having to rush 4 players together for a small timeframe.
I personally like the idea, as the interrupt / weekly rankings were the only reason I played PSO2 after a while of playing it, and since my friends I did that with died, I'm not playing that anymore, lol. Admittedly, it was always a satisfying feeling to see your name on top when trying your best, there doesn't even need to be a reward honestly.
I think for simplicity's sake though, it would be best to just record quest times for the leaderboards page, at least for some popular quests.
For example: