How about a hybrid of two of the suggestions?
The following is what Overwatch does, in actual fact, but I've used the suggestions from this thread to fit it into Elite.
If you disconnect, for whatever reason, whilst in danger, when you reconnect you are returned to the same game mode and instance as when you disconnected. It's forced, and it's the only option available when you are at the menu that takes you to the game itself. Even training is disabled. If you don't reconnect within a reasonable time period, let's say ten minutes, then your account is automatically banned for a short time at the expiration of the relog timer. Let's call that five minutes. If you do it again, the length of time you're banned for is doubled, each time it happens it's doubled again. If it doesn't happen again for a time period, then the length of ban is halved, let's say that occurs every 72 hours.
This means if you have a power cut, you'll probably never even notice you were banned. Likewise if your internet connection breaks, you might never realsie. If your internet connection is especially poor, this discourages you from spoiling the game for other people who end up being impacted by your problems.
Note that this happens whenever you're in danger, so you could tweak this if you decide that combat logging on an NPC is not as serious, for example. Note that currently you're marked as being in danger when you're on the ground at a Thargoid ruin site, so that might also need to be addressed.