First let me just say I hate Eureka and only reason I'm doing it is for the relic. So...

#1. Instead of the chain resetting at 30 let each subsequent kill refresh the chain so the xp, item drop, and light can keep going.

#2. Make the Old areas like Anemos and Pagos more solo friendly. Making it so you can solo same level or 1 level higher mobs without having to spam cure all the time.

#3. 2 Crystals for the price of 1 level of light. (Pagos)

#4. More Crystals from fates.(Pagos)