Sadly, I wish I had more to offer this project. Hopefully I can send a donation here in a month or two.
EDIT: VVVV Okay, fair enough. I apologize if I was brash.
This is one of those times I really wish I wasn't bound by NDAs. Square is known to my client, they have worked closely in the past. They aren't competitors and I believe they are aware of OpenPay already, that's all I can say about that topic right now.
The business side of things such as bringing on Hypercom, Ingenico, Square etc is being handled outside the scope of what I'm doing here, but yes it is being handled.
As far as charging a percentage fee, the fee is paid for by the consumer not the merchant. Hence the fixed fee, however I have considered the implications of 1% fee with a max of 0.01BTC, this is basically the opposite of what you're talking about and the problem with it is that it doesn't provide enough resources to back the insurance program. Charging a 2% or whatever merchant gateway fee like Square, PayPal or Authorize.net is a real possibility and would probably be an important source of income for those service providers, not having to pay any of that fee to the network is a real deal sweetener for them I imagine. Don't forget though, that anyone can be their own service provider. They just need to put up the infrastructure that they want to run and find someone else to fill the gaps.
For instance the reference implementation will include 2 service provider deployments, one targeted at merchants and one targeted at consumers.
The consumer side will essentially turn their MtGOX account into a bank account. They will have their BTC balance and their local currency balance. As the need arises, bitcoins will be purchased to fulfill transactions. This handled through an exchange connector I'm working on, MtGOX really has no part in it. The connector is just automation service that works with their existing API.
The merchant side will feature a gateway application with another exchange connector which is also tied to MtGOX, this is used for clearing BTC balances back to local currency. All a merchant would need is a MtGox account and the gateway app which includes, the messaging component and the exchange connector. No other infrastructure would be needed for them.
Hope that helps!