Hi!
Fluxion is the closest tool to do the Captive Portal attack and at the end give internet connection to the user:
https://github.com/FluxionNetwork/fluxion/wiki/Captive-Portal-Attack

And yes, you can also give them a backdoor with the network update, in this case you’ll need to have some web development skills in order to modify the html page and serve a backdoor to the client.

Greetings!
Diego