They could be written more formally as:

Who does Kim think the coworkers want management to replace her with?

With whom does Kim think that her coworkers would like management to replace her?

Who does Kim think Carol hopes Jim says the coworkers want management to replace her with?

With whom does Kim think that Carol hopes that Jim says that her coworkers would like management to replace her

The grammar in the formal versions is more closely related to Latin grammar, but it introduces a stiffness into the construction that appears to be a dying trend. Forms that, 20 years ago, would have been considered errors, are now accepted practice and come more easily to the tongue, such as:

Ending a sentence with a preposition: Who ... with as opposed to With whom

The split infinitive: They could be more formally written as... as opposed to They could be written more formally as...

...and I am pleased that it is so. I love the flexibility of English, the fact that it is so adaptable, but it does make parsing it hell!

update jporter correctly pointed out that this is not a split infinitive

Clint