I think this would would encourage more full partying up of max level 30 players in general i.e. end game content

and make grinding fun!

When you hit the max level of 30 you would begin earning 1 mark per defeated enemy

The type of mark earned depends on the specific type of enemy you defeat

*note*

Only enemies that are at max level 30 reward marks

The cost of an individual tier 1/2 armor/weapon piece would be 1000 marks regardless of the type or tier

You could "boost" for marks in general by playing with other level 30 players pool sharing marks earned

you defeat an enemy other player(s) get marks at the same time

anyone below level 30 would earn exp on their end instead as usual an do not contribute to gaining marks

Completing missions as a level 30 player in general whether the campaign "level 30 missions"

or duty missions alerts raids etc. "level 30 missions or hard version" would earned you 100 marks on completion as a bonus