There are some turrets that don't deal damage directly, instead they slow enemies down. There is also a problem of no longer useful turrets that could be crafted into something else but cant because they gained rank.
Adding something that would allow us to "extract" these kills/damage and then transfer them to some other turret would solve both issues at the same time. To make it balanced, you could make that transfer only 25% efficient or so. What do you think?

Howdy!

For turrets that now have a rank, you can set the kill counter to disabled and then place down and pick up your turrets. That will reset their ranks.

In regards to transferring kills that does sound interesting! I'll have to consider that for a version 2.0 release if I ever get to it. Currently this is just a port of the original mod with some tweaks.