devtrackers.gg
Just some basic consideration while you're coming up with this plan!
1) Reducing the Combat Mission tiers to 5-10 helps consolidate the playerbase. This helps queue times for faster, more consistent matchmaking.
2) Players are very aware that 5 is a bigger number than 4, and that 10 is a bigger number then 9. In general, players are drawn to the biggest number available, be that Tier, Health Pool, Damage, and more... So lower tiers are already fighting the inertia of players that want to move onward and upward.
3) Lower Tiers have less consumables and poorer stats in general, as they are weaker ships. A lot of folks play Tier 10 for the best-in-game accuracy and other characteristics, so a lower-tier incentive would like need a complete change in terms of range/dispersion/gameplay.