-1
The reason why it is not fruitful in the end as it opens up opportunities for possible trolling and time-stalling for the player on the other end.
I am listing some cases in the following:
You disconnect in a battle and you decide you wanna let this one battle slide cuz you maybe have some work to do, but the opponent has to hang around for another 2-3 mins(guessing you're also suggesting a timer for the reconnect window) without anything to hear from you, which is borderline disturbing for them.
Another point would be someone who is gonna deliberately troll their opponent. Let's say, your opponent disconnects once(implying on purpose), then returns after 1-2 mins plays for a bit, then again goes off for a bit and on and on and on.
This here also suggests that, if this is implemented, the PvP rules would need a revamp around stalling and others, which in showdown is non-existent for casual plays.
Conclusion:
Overall it is not worth the effort and a good step to prevent yourself from disconnecting would be to get better internet, it is fairly cheap nowadays and with 5G in the play even better. Suggestion would be to play PvP during suitable internet conditions. Also something you may or may not be aware is that the game already has a reconnect window of 1 minute, I believe, not really sure of the exact time but it is just enough and has helped tons.