Can you clarify if you are just reversing the constraints so team is constrained by owner, or do you want the Owner constraint by team to still be in place? If the former you might be able to do this via picklists alone, but the ladder would need some form on business rule to drive the behavior in the background and you may find you have to leave Owner un-constrained for it to work.
In an ideal world we wanted the constraint on both fields:
If I picked OwnerTeam I would see the 10 team members in the Owner selection box.
If I picked Owner I would see the 4 teams in the OwnerTeam box.
Understandably, leaving OwnerTeam blank, then choosing Owner from 100 staff, then OwnerTeam (of the 4 for that person), the constraint rule would likely wipe out my Owner and present all 10 team members again.
We played with this but seemed to get caught in such a loop and we gave up. It's as if we need an "Only execute if Owner is blank" rule within the Owner constraint.
Any pointers you have are always welcome! Mark.
That makes sense that you got stuck in a logic loop. Constraints are all or nothing, they are not selectively applied with is what you'd need to do this with just two fields.
The only thing I can think of would be to set up additional fields for the reverse case with picklists that constrain the opposite way and show/hide them on the form as needed. You'd then need to build logic to cross-populate these on save or something like that.
You could hit the Uservoice portal with a feature request form conditional picklist constraints but I'm not sure if Product Management would go for it just due to the interesting behaviors it could introduce.