standard practice is/should be try scorer brings ball back with him/her/them
Yes, that's fine for some forms of try scoring, what about when its a kick ahead and the player forces a loose ball in-goal? Often the ball ends up bouncing away or getting kicked away. That might be OK in a stadium where there are advertising hoardings, but what about in the weeds where you can have half a dozen playing areas on a field?
I prefer what didds suggested, which is what they do in the NRL - the time goes off after 60 seconds but the kicker is allowed to complete his kick.
In fact, I would go even further than that. For kicks at goal, I would have the clock stopped the moment a try is scored, or in the case of a PK, when the kicker or captain signals the intent to kick for goal. The clock remains off until the restart at halfway or (for a missed PK) on the 22m.
Also, we could do away with the pointless Law that requires the same ball to be used for the conversion that was used to score the try. In the elite game, the kicker could just get a new ball from the ball boy.