This sounds fun for like...5 minutes, but if you think about it for longer than that, you realize this makes dealing with urn incredibly non-committal and less interactive. It makes it far less useful to melee someone for the urn, since they'll just chuck it before you can force them to drop it, making it difficult to intercept in transit.
It is also highly advantageous to air movement teams like Lash, Celeste, Viscous/Apollo to some extent, because catching the urn mid-air prevents the enemy team from intercepting it at the landing location.
Couple that with the need for the urn to come back down and you could theoretically throw it from one urn deposit to another simply by learning the throw angles at specific points-completely removing the team interaction & counterplay to the urn mechanic.
Full Disclosure-I don't like the urn mechanic as it exists in the game currently, and the objective needs an overhaul or change, but adding urn throwing into the mix would make it way worse.