I would like to recommend adding a battle pass that can be purchased by platinum.

1. daily login until 30 days
2. task completion rewards
3. pet rewards
4. mythic items / arcane items
5. unlocked chests rewards
6. etc. (open for suggestions)

Note: This will encourage more players to buy platinum at a minimum fee and the number of players online will be increased too.
Got this idea from other mmorpg games.