In home audio, there is really no reason to do this. More is not better. Simply, the two Tweeters will be interfering with each other.
It is possible that you won't notice it.
Regardless, from a standpoint of "best practices," it is not advised regardless how you wire it.
If you did wire it correctly in series, you are correct that the impedance will double rather than halve and this will not be destructive to the equipment.
End of the day, it is your system. Enjoy.