are you planning then to go code first? Will you need to regenerate ever again ?
If you know the answer to those questions. Or have at least considered the impact.
See Reverse engineer code first to existing DB
This gets you a model you can start with
OtherWise: The partial class approach may help. Last time i tried (EF4) the generated code was partial. You leave the generated class alone and add a partial section
public partial class MyGeneratedClass : SexyBaseObject
{
//...
}