the whole challenge part seems well structured and all, but i think you are completely ignoring the fun part of the game. maybe ross and twenty other skilled sectorers/players will try and enjoy the super-complex maps, as much as (more) i heavy grinders will enjoy raching 130m exp for the level cap
but what about all the other players?
i, for example, stopped playing also because bc became endless grinding over and over the same map with the same methods. it can be fun at first but if theres little less cohesion between players or after some time it can become boring and old.
i was just thinking, if there was a game mode where the point isn't to mainly kill mobs over and over it would add some fresh gameplay.
for example a race mode (buffed and developed so it's more challenging and less plain than what you can actually do in the game atm).
also difficulty doesnt only come from mobs, but also from environment (like some pvp maps), it would be nice to have new (or partly atleast) maps in that way
if one update only had to take place the sector one seems the best since sector is the most played mode. but if the pvp/bvb update would be effective enough to refresh and make those modes more popular i think it would be very preferred