I'm personally in the camp who would prefer that lost coins be left where they are whether they're vulnerable or not, but I won't really mind if they get destroyed either, considering the scale of damage their theft may cause.
The original chain will remain the strongest chain. If some groups can reproduce the privatekeys of 'shalecoins', it's their reward. They are trying to build a computer in the near future, that wouldn't be built so fast without that incentive. That opportunity accelerates the technology. If there are still some BTC owners with old addresses and remove their coins now, they will be secure. So it's a fair game.
The Bitcoin network is a pure competition network. Only the best technology will be successful here and make it secure. A Bitcoin fork without the old coins would be like another s**tcoin, because it would avoid real competition.