Put a hard limit on clauses that may be severed without invalidating the entire contract. Two, perhaps. Three strikes, and you're out.

>What if the contract is complicated and you end up having part of it invalidated in court?

Sounds like a feature, not a bug. Contracts have to be simple. If you can't do the transaction with a simple contract, you have to find a different method to carry out what ever is desired to be done.

I'm sorry, but this is a ridiculous statement. This isn't just about labor contracts. Contracts between businesses need to cover lots of different eventualities and edge cases. They need to acknowledge and adhere to a variety of laws, depending on the jurisdictions involved. Disclosures must be made. Eventualities must be planned for. Nobody (for the most part) wants to go to court to resolve something that could have been headed off in a contract.

Perhaps contracts between businesses and individuals, or even just businesses and consumers, should follow different, simpler rules than contracts between businesses - especially mega-businesses?

Let businesses with hundreds of staff attorneys do whatever they want to each other. But keep them from beating up a guy who just wants to collect a paycheck or buy a simple service.

Whether it's in the contract or not, you have to go to court to enforce it. There's no other authority.