I definitely agree with this. I also think that capability systems that are based on a good type system are probably going to be easier to code with than ones

I definitely agree with this. I also think that capability systems that are based on a good type system are probably going to be easier to code with than ones based on message passing security. The type systems make it easier to define and use the basic capabilities and involve a lot less boilerplate code than what one sees in other variants of capability-semantics.