If the block reward is intended to be stable by time (not blocks) then the algorithm should be changed to not have difficulty as an independent variable and instead use time as the independent variable. That could be an EIP just as easily as this one. By conflating these two issues, you are conflating discussion about them. As an economic participant, I am an advocate of removing the difficulty bombs entirely and also of reducing the block reward. Rather than having 4 EIPs with all 4 combinations of such, we can have two EIPs that are isolated from each other and can be evaluated and discussed separately.
We have seen discussions around block reward/difficulty bomb EIPs degrade in the past and this is partly because they keep getting proposed as two-in-ones like this.