Snivy is redeemed, Swadloon had two victory's last time and Oshawott hasn't had an offical second gym lost(tie is a victory/lost in my eyes), and Roggenrola get's it's first gym battle and evolves...Again Tranquil fan's, there are better suit pokemon from this gym then her
I like your ideas, though I don't see Swadloon being used unless it's evolved beforehand, and that certainly seems unlikely. I also don't really think Tranquill has a huge chance of being used, but I think it's the fourth most likely. The only Pokemon I see being used in more than one Gym are Pikachu, the starters, and possibly Scraggy and Tranquill. I see the final tally being something like this:
Pikachu - 5 (Cress, Burgh, Elesa, Skyla, Iris/Drayden)
Tranquill/Unfezant - 1 (Skyla)
Oshawott/Dewott/Samurott - 5 (Cilan, Lenora, Clay, Brycen, Iris/Drayden)
Tepig/Pignite - 5 (Chili, Lenora, Burgh, Brycen, Iris/Drayden)
Snivy/Servine - 4 (Elesa, Clay, Brycen, Iris/Drayden)
Scraggy/Scrafty - 1 (Iris/Drayden)
Swadloon/Leavanny - 1 (Burgh)
Palpitoad - 1 (Elesa)
Boldore/Gigalith - 1 (Clay)
This does leave a few spots open for any more Pokemon Ash may catch.