I won’t speak of any vertical progression here because I am fine with my progression and having fun with each tier.
I can think of daily or 2-day events which are just personal and happen twice a week or so.
One is speed-killing contest - in this there are tiers depending on dragons den level where players with same dragons den level can compete how fast they can destroy fixed AI generated bases with single dragon and the best flying time is recorded . Leaderboard players get decent rewards while player timing progression earns them normal rewards like personal prizes.
This kind of event can be implemented in different variations related to specific dragons ( preferably lineage).
This kind of event would boil down to skill and the player’s roster.
This can in turn also motivate players to max out powerful dragons relative to their base level .
(Just a thought, sorry if this is repeat of an old event or another proposal.)