I'd like to see some foldable propellors for the Phantoms too, like on the Mavic. I know some third party have them for the P1-3, but I haven't seen them for the P4 yet.
It is not just about ease of use during transport. I also think foldable props are safer, because if they hit somebody they will give way instead of cutting people. Maybe even make a rubber strip on the front.
What do you think?

I would buy this.

They're heavier and make the drone unstable. Not good battery time

If the propellers are moving at full speed, it's not going to make much of a difference. In addition, the change in propellers could potentially cause performance issues, like Jack Fedele indicated.