The whole point of hiring a team is that you aren't evaluating individual performance or skills; you're evaluating the groups' performance and skills. If the team is good, the people who can't immediately be helpful will re-train so that they can provide skills that are useful in the new context. The team will evolve to become the exact team that you need.
That seems like a best-case scenario to me, unless the team is 3-4 people and someone is looking to create a capability or product from scratch.
In theory, yes, some actions are 'not allowed'. But this isn't an mathematical excercise it involves real people.
e.g. Who get's told the 'offers'? Do they get separate salary offers, or is it a single pot? If the latter, how do they decide what's fair? What happens if evereyone's extremely happy but one person? Or two people? What happens if there are competing offers that different members perfer unequally? How do the ongoing salary reviews go? Can individual members be fired after being hired?
It's going to be very messy, and I would imagine may not work a good proportion of the time. I would imagine a lot of the answers of the above questions would start looking like the answers given by a union, something that the tech community as a whole has avoided so far.