This message brought to you by the legal concepts "reasonable man", "attractive nuisance" and "booby trap".
The first problem is that you are advertising the SSID. That is, when Innocent queries "any WiFi networks in the area?", your system is jumping up and answering "Yes! Right here! My name is Malicious_Wifi and I am open."
First, if you do not desire intrusion into your WiFi network, you are granted ample ability to lock it down:
- you can fail to advertise the SSID (force them to know the SSID)
- you can use WAP, WPA etc. to set a password on the WiFi
- you can have an "open" WiFi but one which answers every HTTP request with an interstitial logon challenge.
By doing none of these, you are inviting connection. Now your grandfather with no computer experience, in your small town, might have a case against weird people parking vans on his street to poach his Open WiFi becuase he didn't know how to secure it. But as a techie you have no standing to criticize. You have created an attraction.
If you use the UI's of many mobile devices, you know it can be awkward to control them precisely; for instance it may pop up an interstitial inviting you to jon Starbucks WiFi, then 50ms before you actually tap it, change the interstitial to inviting you to join Malicious_WiFi. tablets do this accidentally. This stuff is not safety-engineeered because the industry philosophy is "features before bugfixes" or "move fast and break things". And of course, people don't really pay that much attention. So this kills your presumption that everyone who joins your network has mens rea, a thoughtful intention to do so. You are at too high risk to snare innocents, which is why I call them "Innocent" instead of "Curious".
If you have a spooky old house or installation which attracts the curious/urban explorers, and you make efforts to secure it but they keep breaking in anyway, and it draws crime or there's risk of getting hurt in there, that is called an attractive nuisance. This increases your liability for what happens in there. You don't become criminally liable for cooking meth, but you certainly will be civilly liable if somebody puts their foot through a faulty stair.
That's not normally the case. Once a criminal broke into a house, and tried to exit through the garage. The interior door locked behind him, and for some reason (gross mechanical incompetence?), he was unable to open the garage door. He subsisted on large bags of dogfood and bottled water. He sued the family for his misery, and lost, because it was happenstance and not an intentional booby-trap. It met the very minimal duty of care every facility manager has to first responders and trespassers to not leave the most gross hazards unguarded (open pits, rotted stairs, exposed electrical wiring) etc. You know sometimes, people get in trouble with that standard, with pools.
Obviously, this "duty of care" excludes booby-traps. If you intentionally create a hazard to a trespasser, then you have crossed the line from negligent to malice aforethought: here it is you who has mens rea. You are criminally accountable for the trespasser's injuries same as if you attacked him in the street. Indeed, when Fort Knox type places use booby traps, they merely contain the intruder long enough for security to capture her, and they have a system to positively alert security immediately before the trespasser needs an insulin shot.
How does this apply to your situation? From the reasonable citizen's view. You will find it very hard to seat a jury who will consider it a despicable act to log onto an open WiFi. They will consider your hacking to be a wildly disproportionate response, and not a response at all, but the origin crime.
They will consider your hacking in this context to be a "booby trap", again a crime all its own. Yes, I realize your idea makes sense from inside its own bubble. But the view from 30,000 feet is this is just a slight variation on other Trojan horse wifi networks which seek to infect other systems for nefarious purposes: it only differs by using a cutesie name for the SSID. And even that makes sense: there's a reason phishers still claim to be from Nigeria and swerve out of their way to do so. You look, walk and quack like an actual Trojaner.
"I'm the bad guy?" 'Fraid so.