I don't think (i) doesn't make sense to me... I guess a package could foist a TS dependency on you but it certainly doesn't have to. It's pretty sloppy if it does, so maybe not the greatest package anyway. (ii) has nothing specifically to do with TS. (iii) agree. (iv) sure, though static type checking requires a static type-checking step and tool.
You started by skipping over the benefit of static type checking, but that's the direct trade-off: is that benefit worth the extra complexity and time spent satisfying the compiler. For me it's probably usually yes for smaller projects where I know the devs can handle it and definitely yes for larger projects where the communication burden is high (it just partially helps people stay on the rails, organized, and on the same page -- not sufficient by any means, but it eases the strain).
You started by skipping over the benefit of static type checking, but that's the direct trade-off: is that benefit worth the extra complexity and time spent satisfying the compiler. For me it's probably usually yes for smaller projects where I know the devs can handle it and definitely yes for larger projects where the communication burden is high (it just partially helps people stay on the rails, organized, and on the same page -- not sufficient by any means, but it eases the strain).