If your switch will NEVER be connected to wifi, why are you concerned about bans? Do you have a Switch Account tied to the console? I assume not, if you were never online.
My experience has been that on my console with NO user account tied to it, Nintendo sends me over the air game updates automatically for every game I have installed (NSPs). I haven't tried inserting one of my legit cartridges to see if it auto updates, but if Ninty is updating my illegit NSPs, it would be nuts for them not to update my legit carts.
I can't tell for sure if my console is banned, since I have no account and thus can't actually connect to anything that would tell me "hey youre banned", but the updates keep coming. I even had some sort of corruption after installing with SXOS and the game had a cloud icon over it... It said the game needs to install missing files before it can run. So, I clicked yes, and it installed the missing files (from Nintendo's servers) and the game was playable. Hollow Knight, if you're curious.
I've heard that all bans are CDN bans now, and if I was CDN-banned I can't see why they would continue sending me OTA updates automatically. Thus I presume my console isn't banned, which is pretty nuts. Or maybe it is banned, and it doesn't matter because I can still do anything I want on it. Either way...
In short, if you aren't online and never will be, you must not be afraid of banning. So how about just try enabling the wifi, but with no nintendo account, and see what happens. Worst case scenario, Nintendo bans your console and you get no updates, in which case just continue as you have been. You are "self-banned" anyway. Best case, all those updates come flowing in with no effort on your part, and maybe you don't even get banned.
I wonder if Nintendo has no way of telling that I don't own the games, since I have no account, so they don't autoban me. I presume that in the fabled future CDN update, they may tie console certificates to owned games via a database query, in which case they will almost certainly ban your console if you try to download stuff with a cert that doesn't own the game. But, they aren't doing that yet, which might explain why they keep sending me updates. Even then, Nintendo has no way of knowing whether you own the cart or not, since it is a physical object, and banning you for trying to download an update to your cart while staying logged out would be NUTS, even for Nintendo, and would be a messed up policy change for people who don't like having nintendo accounts, or buy a Switch for their kids and only use local accounts. Imagine if your kid, with no online account, tries to update their legit cartridge of mario kart and the console gets banned. I don't think they would do that, ensuring that cart updates should be possible for all consoles, with or without accounts, until such point as they start requiring nintendo accounts just to download updates to carts!
And if you are hoping to eventually go legit (if never isn't never?) and wipe the switch and go online, everything I've read thus far says that's a pipe dream. If you've used homebrew or pirated you can just assume you'll be banned eventually, at least if you are using a Nintendo account, right? Don't worry about it.
Try it! You don't really have anything to lose, imo.
