I wouldn't drill the lid for a thermowell and ball lock port. There are a combo action of items on Amazon you could get and utilize the bung hole that already exists.
Homebrew #7 Stopper Thermowell
Stainless Carbonation Cap Counter
Drill a 1/4" hole in the undrilled stopper for the carb cap and you have a ball lock connector.
The bung with the thermowell works great on my anvil fermenters.