With raids that make it so your creatures level are lowered to be in line with the raid bosses, so all the arenas should have level and boost caps. All the lowest arenas should have no boosts at all.
This is a way to keep a player from gaining a high creature and steam rolling over people with it. It also keeps lower players from boosting one creature to steamroll over other players when ever it is picked.
This will also give incentive to level into higher arenas although this is a natural occurrence as you grow teams.
This won’t stop droppers but it will keep droppers teams at a level where players in those arenas have a chance and can get some take downs. You shouldn’t see a boosted level 30 Thor in Sorna Marshes taking out players in 3 chomps.
This would be an arena cap example:
Arena 1 - Level 6 - No boosts
Arena 2 - Level 8 - No boosts
Arena 3 - Level 10 - No boosts
Arena 4 - Level 12 - No boosts
Arena 5 - Level 14 - 6 Boosts, 2 per stat
Arena 6 - Level 16 - 12 Boosts, 4 per stat
Arena 7 - Level 18 - 15 Boosts, 5 per stat
Arena 8 - Level 20 - 18 Boosts, 6 per stat
Arena 9 - Level 22 - 21 Boosts, 7 per stat
Arena 10 - Level 25 - 24 Boosts, current rules
Arena 11 - Level 29 - 27 Boosts, current rules
Arena 12 - Level 30 - 30 Boosts, current rules
Arena 13 - Level 30 - 30 Boosts, current rules