Nothing will change. The comp that wins most of Ranked matches right now on Bastion will most likely be still the dominant comp. You can replace the PT with another dpser and it still work fine as well.
1. Sorc Heal
2. Operative Heal
3. Jugg Tank
4. Sin Node Guard
5. Smash Marauder / Carnage respec for few maps
6. Smash Marauder
7 . Lethality Sniper
8. Pyro PT
I agree, I do think though puting in a sage dps or adding a vanguard tank could work.
Far as the others guess it would be preference more than anything, some guilds won't be comfortable rolling any other spec that is unproven due to pride.
That would not be my method, but whatever floats your boat.