I think the time wasting could be solved relatively easily. I put a post up the other day… if you don’t have treatment on the sidelines it’s a minimum period before you can come back on. Say 3/4 even 5 minutes. Soon stop them going down if their team has to play with ten men for a proper period instead of being waved back on instantly.
I think there's a much easier solution, just stop the clock and do away with injury time.
Whenever there is a major stoppage, injury, penalty, attacking free kick etc just have the referee stop the clock.
Then book people properly for time wasting, yes it's a soft yellow card but it's ruining games.