>But there are a literally limitless number of way to extend the trust of the base layer, up to any and all other layers. Ark is a great example, all transactions off chain, every single user has unilateral exit ability.

Unilateral exit will be too expensive for most users to enforce. I don't think this is the framing that should be used. 

There is simply no way to scale the trust assumptions of the base layer to every other layers. 

Tradeoffs are necessary and desirable, anything else leaves us operating inefficiently and burdens individuals with undue costs.