This is how Factorio works. It already has the equivalent of such a tag - data-final-fixes. But when multiple mods use data-final-fixes they cannot all be the last one, so this happens.
I am reluctant to add optional dependencies to all mods at this time. Maybe to the bigger ones.
Factorio 0.17 introduces the hidden optional dependency. When that comes out I will feel better about adding more dependencies.
While not ideal, as a workaround before 0.17, I suggest manually adjusting the dependencies - something quite common when creating a custom set of mods.
And as a side note, I am not going to go through all mods in order to consider whether to add them as dependencies. If someone (or a group of people) lists such mods somewhere (like here) it will make the process easier (and faster). However I want links to the mod (if extensions are applicable - links to them as well).