I think having open slot secondaries is better than having nothing. We have fixed secondaries with IR3, RS3 etc. and I think having a secondary with only 1 open slot is enough, because its not a primary so it does not support more mods.
The currently available weapon modifications should have different values when added to secondaries, you are not shooting with an assault rifle
Here's an example: It is better to have one slot for modifiable secondaries in my opinion. This won't make them much more powerful.
Ex. .45 current dropoff range is 40m with improved rifling dropoff range is increased to 50m. Extended Mag 3 increases clip size from 7 to 10 bullets. This picture is just a sample from Open Test World.
You have different opinion? agree or disagree? share your thoughts.