After installing the system, all that would be needed is pacman -Syu and the system should be ok.
So if you uninstalled any gpg package, just install it again.
There is nothing bad running populate even if you think is removing unecessary stuff. most of pacman-key commands are safe and don’t destroy the system; in fact we are the ones that destroy it 
(talking by my own experience)
some gpg related packages you may want to try reinstalling
sudo pacman -S openssl openssl-1.0 gpgme --needed
or even
sudo pacman -S base base-devel --needed
The commands above won’t work if you removed the files manually with rm command