The problem with this is that it requires us to trust our intelligence agencies, but they have shown themselves to be duplicitous, quite willing to lie to congress under oath, and unworthy of trust. Even by their own admission they have not been taking these actions when they have extreme certainty - people are killed who are "not specifically targeted".
There is no way to make assassination without trial by the executive transparent and accountable - that's why we have a court system and independent judiciary, and a whole host of laws protecting the accused. Subverting that entire legal system is very dangerous and we shouldn't allow it, because if we do, there is no legal impediment to stop laws used for terrorists being turned against others who oppose the state.
It feels like this is one of those polarizing issues where each side is too scared to admit advantages of a different point of view in case they lose some ground. Everyone takes an extreme view for/against, the debate doesn't address the finer points of reality, and no one changes their mind or comes to more reasonable compromises.