You can also use MutatingWebhooks to inject initContainers or side cars to achieve that pattern.
MutatingWebhooks increase the runtime complexity since you're jamming more config in but they can handle vendor/3rd party software.
Depending on the CNI, insecure TLS flags might not actually be that bad. There are some CNIs floating around that can handle encryption. In addition, software defined networks like AWS might not offer encryption but they do guarantee messages are authenticated so you can trust the source IP