First, I have only started replaying the game last November but it seems that Defense wins should be rewarded with maybe 1 or 2 coins since some players run different attack builds from their defense builds. Otherwise Defense wins/losses really on affect rankings.
Second, if you have a rematch with someone because you lost then it should always switch between the two as to who goes first.
Example
First Attack Match - I went first but lost the match
Second Attack Match against same player - I would go second automatically
Builds needs to be able to defend as readily as they are to attack. Especially since Defense wins/losses affect your ranking, but if the RNG always falls in favor of a team built to first round kill then they can win multiple times and even remove your chance to overcome. I know I have lost 2-3 in a row trying to attack the same player, because I kept going second and was 1 rounded.
This would only apply to attacking the same player if you attack a new player then it should remain RNG.
It may have been discussed before but just my recent observations as a return player.