One way to solve low quality shareholder problem is obvious but not talked about (at least I haven't seen): let DAO have a right to confiscate shares from shareholders. If there was a bad situation where everything has stopped and nothing gets done, easiest solution would be, of course, to destroy the opposition. After the shares from opposition have been confiscated and redistributed/destroyed, DAO can work again.

In reality confiscation would be used very rarely, if ever. It would be enough if shareholders were aware of that possibility. Those who disagree would sell their shares before any bad conflict would arise.