I would love a mod option "Landfill only on shallow water yes/no". This way you can use landfill to straighten your shoreline but not to cheat a whole island in the ocean far away from the enemies. What do you think?

There was a mod for 0.17 that could help realizing this https://mods.factorio.com/mod/LandfillRestriction
This mod disallows landfill placement in deep water

Thanks for the feedback i do like the idea and it is already implemented in the development build. I will probably release it along with other tweaks tomorrow.
Have a good day!

You can now toggle if you only want to landfill on shallow water in version 1.0.5.

:-)

You could write down the default options somewhere so that users know if they can take your mod out of the box or there is any need to reconfigure it.