Your current line up scored a decent amount of runs and took it close to one of the stronger teams in the league. So the conservative approach would be to stick with it and see if the team can edge out the next team. The aggressive approach would be to shuffle the batting order further to get the best out of the non performing players.
Dilscoop advised not to go with more than two front line bowlers and 2 all rounders. If you follow this then the equation becomes a little simpler... Swann and Johnson could be your front line bowlers, Nathan, Dilshan and Duminiy could be the remaining bowling options. This way everyone bowls 4 overs and you can get the maximum out of Swann and Nathan.
The batting is a little complicated. I am still trying to figure out how the simulation works. It seems there is a tendency to collapse at the end of the batting with all teams. Now I am not sure if the collapse will happen regardless of who you put in or is it because the stats are not good for those players. So the safest thing to do is to put all your performing players in the top 6 to hedge against risk and then also put the non performing batters in the lower order to see if you can get the tail firing with the bat to get those extra 20 runs. Your original strategy was to bat opposition out of the game so we need to get the batters firing at all cost since you don't have much options with the ball.
Following that reasoning this is what i could come up with:
6. Guptil (putting them here might avoid the collapse)
In the real world with 9 specialist batsman there should not be any talk of collapses but this is a simulation so...