Is it possible to create a multi-server SharePoint farm in the DMZ without using a domain?

I am working with a client to plan a topology for a public SharePoint site.

The SharePoint installation will live in the client's DMZ, and the plan is to use the existing SQL Server machine to host the SharePoint databases.

The problem is that there is no domain in the DMZ and the client does not want to create one without going through the proper planning process.

As far as I understand, there is no way to set up a multi-server SharePoint farm without using a domain account to initially connect SharePoint Central Administration to SQL.

I'm pretty sure (and tried this) that you can't use SQL Server Authentication to connect the farm to SQL Server when you first provide Central Administration with the Productions and Technologies Wizard.

My other option is to install a single server, recognizing that this limits our future growth should we ever need to add another WFE.

thank