How suitable do you think SilverStripe is for modelling a bidding process? Users with different access privilleges would see the process depending on their role. Different kinds of media, users and companies would be attached to the process.
The business case is question is Carrotmob Finland. Carrotmob organizes consumers to make purchases that give financial rewards to those businesses who agree to make socially beneficial choices. See video for a brief description of the idea: http://www.youtube.com/watch?v=LUz0kM1u_jk
I would say go for it. I have done a lot of work with SilverStripe, and really confident in it.
The sapphire is is highly reliable, and as it is a framework you will be able to do your coding stuff more easily saving loads of time.
And as the ORM is implemented you dont have to worry about how to run queries and stuff, Also you will benefit a lot from the CMS backend.
Also you can enjoy lots of help, you can use the forums, and the IRC for help, and the documentation too which is brilliant.
I can find a lot of advantages in Using SilverStripe for such a large project.