Putting nginx on the internet isn’t an issue. It’s designed exactly for that purpose.
A reverse proxy means that no one talks directly to the piaware device.
At least if the nginx is running on another machine.
I’ve removed the airframes.org stuff in tar1090 i believe.
So feel free to give that a go: GitHub - wiedehopf/tar1090: Provides an improved webinterface for use with ADS-B decoders readsb / dump1090-fa
Also easy enough to set up nginx directly on the RPi and serve tar1090 with the nginx configuration file the installer creates, all you need to do is include it in your nginx config.
You could also serve Skyaware from nginx without issues, the configuration isn’t hard.