There is no freedom of contract issue--getting rid of "work for hire" doesn't mean employees can't contract to transfer their IP to their employers. It just means that these transfers must be specific and explicit.

Having done a lot of work-for-hire in film and TV, my experience is that it usually does involve specific and explicit contracts, and disputes are most likely to arise on amateur productions where business is one on a handshake or informal basis with no paperwork involved.

I'm no fan of 'submarine contracts' but more often disputes like this tend to involve someone (such as a camera person) holding the IP hostage as leverage in a payment dispute. Whether a project will be financially successful is often a matter of pot luck, so many people just sign whatever comes their way and don't review the terms unless a dispute arises and the stakes make it worth winning. For one thing, you can't make people read contract terms carefully and a lot of creative people don't like reading turgid legalese in the first place; for another, the ratio of paying producers to wannabe creatives is low enough that many employment offers may as well be contracts of adhesion, and until people achieve enough success to get an agent the attitude is often that it's better to sign a bad contract than to be passed over for someone more accommodating.

Maybe I misunderstood what sort of work for hire situations you had in mind?