Depends on how you'll use it.
If you're making full backups of your own games and placing them on MIG Switch, therefore using MIG Switch as intended, you'll be good.
However, if you intend to use publicly available dumps (preferably full, not mixed i.e. XCI and initial data from one game, the other certs from another, donor game), there's a risk that you might get your console banned, especially if there's someone else playing the same game at the same time. I'm not sure if staying offline matters in that case, not sure if telemetry collects data about when and which game you've played. If your console is banned, you'll be able to get game updates: 1) if they are available on the official cart or 2) by matching the version locally with another Switch that has the game on a higher version. DLC, however, will be available only if it's on the cart already or you've legally downloaded it from the eShop before you got banned. Note that, even if your console is banned, you can still and will receive firmware updates.