I don't think your suggestions would help matters.
1) Losing your ship results in losing far more than 15 minutes game play, so the benefits of combat logging still outweigh the punishment you suggest. Nobody is going to choose not to combat log because of this. You would be penalising a wide section of the ED player base without actually affecting the behaviour you're trying to stop.
2) Penalising people for playing in Open is only going to result in fewer people using that game mode, which is not a good result for anyone.
Combat logging itself isn't the problem, it's just a solution players have found to deal with other issues. Ultimately, the problem with Open is that dying has a huge effect on your gameplay. You're likely to lose hours of progress, and so people are rightly afraid of being killed. Introducing extra punishments isn't going to help matters.
There are only two solutions that I can see:
1) Reduce the consequences for dying.
2) Reduce the chances that you will be killed in Open.
Both solutions are possible. For the former, all you would need to do would be to reduce insurance costs. For the latter, increase the variety in Open Play so that there is something else for CMDRs to do there other than gank each other.
Reducing the consequences for dying would seem to go against the 'dangerous' nature of the game, so that would probably be somewhat controversial. If you want to encourage PvP then you just implement Pilots Federation insurance whereby insurance costs are reduced if killed by a fellow player. That balances the increased likelyhood of being killed by a player with the increased consequences of being killed by an NPC, which then stops people being paranoid about PvP without affecting the PvE game balance.