I think that it should 100% be upgraded to a red card. Yes, it would be very hard to enforce. But my reasoning is not focused on the enforcing of the new law. Its already not enforced enough when players are deemed to have “tripped” when it is very clear that they have dived. Prevention is better than the cure.
By increasing the punishment to a straight red card, you put in the back of players’ minds that if they dive, they will be sent off. Not only that but they will leave their team a man down, probably not get paid (if they are at a professional club, us amateurs do not get paid of course). The only reason punishment exists is because people do the wrong thing. If no body does the wrong thing then nobody gets punished. It’s the same for football if nobody simulates or dives then nobody gets sent off for it.
I believe that by making it a send off offence you would reduce the occurrence rate significantly. There will always be a few who try and push the boundaries, there always is but they would be few and far between. It will not stop it in all circumstances. Title deciding league games, Grand finals and Cup finals where the reward may outweigh the risk especially late in the game or in extra time. But these games only occur maybe 5 times in a year.
In conclusion even though it would be hard to enforce, I think its 100% worth it because it would dramatically decrease the amount of players diving. Therefore improving the image of the sport.