Well, im just start playing the game for 2-3 days and everything goes smooth so far. (thanks to @InterAction_studios and team)
But; i have an Idea. How about adding Skill Tree feature ? Just like Adventure/RPG games; which player earn 1 Skill point when he got level up (Tier up in this case!)
And with those skill points, player can obtain bunch on Unique features; like:
Unlocking new weapons and satellites
Increase overall Damage rate or Key drop rate
Extend maximum of Fire power or Fire Speed
Unlocking new Paint job for spaceship customization
I don’t feel like locking features behind both playtime and keys is a good idea. Also even if the levels only went up to 99 like tiers, it would make getting on the leaderboards with lower levels extremely hard.