@Rabob;

The total war support cost becomes 26%, which is easily mitigated by using "War Propaganda". This in turn drags the penalty down to roughly 13%, provided you run them in parallel.
Now, this is only available during non-offensive wars, and it's also only available during times of low war support (sub 50%).

Considering the decision is unavailable during wartime the whole idea of the negative war support is to simulate a populace that grows weary of war when integration occurs.

I might play around a bit with the values, possibly bringing it down to ~15-20% instead, but I'm currently not particularly invested in HoI4 after finishing my last game.

I see your concerns and I'll think about re-balancing the mod, but I refrain from making any promises as of yet.

would it be possible to core colony states too? they never resist(as far as I know), so maybe they would need a different mechanic? Like it costs less but takes longer? idk for sure.