I think the big problem in all of this is the implicit type conversion that powershell does during runtime. It makes any system you can think of break apart as soon as you interact with code that hasn't been "type-annotated". Many of the benefits of static typing go away when my function needs a string, you pass a hashtable via some 3rd-party code and then i receive "System.Collections.Hashtable". Same goes with array packing/unpacking.

You could honestly solve like 90% of the problem by just adding an engine flag to powershell that disables automatic type casting and an engine flag that disables automatic array/singular conversions and then use psscriptanalyzer to warn on places where the types (and pluralities) dont match perfectly.

This doesn't help with functions that take pscustomobjects but you could imagine extending the type-annotation to require specific properties on the objects being passed in.

As a note -- the lack of static typing causes a huge number of bugs in "powershell as an application" use-cases and it's the primary reason (secondary being performance) that we are actively removing powershell as an approved language for application code.