It's a controversy, if repair this with a glue that it's not tough enough, it will fail soon, but will preserve the original parts, if you use any kind of epoxy glue, you won't be able to repair it again.
What would i do in your case: First disassemble the whole speaker an than take note of everything, the cone hardness, the voice coil (Number of turns layers, kind of wire, kind of material etc...) and try to copy, from the scratch, you will get a lot better result doing this. I tried to repair many many speakers, but the repaired speakers is not as good as the ones i use new material to repair, even the speaker has flat wire on the coil, you can use round wire, the difference is not that big, considering you repairing and old coil versus a new one. If the original coil is made of aluminum, you can change to Kapton or fiber and have a more eficient speaker.
In any of cases you will have to re-measure the Thielle-Small parameters to ensure all the parameters of the speaker.
Hope this helps
Best Regards
Lira