The intent of class E is to separate aircraft in IMC. Surveillance or non surveillance is secondary, and would be dependent on traffic and availability of the equipment.
If a VFR aircraft requires a transponder in Class E airspace, I would argue that the intent of Class E airspace is for it to be survielled, Not a crack at ya, obviously Class E can be done procedurally but I don't think I'd want to be mixing it there without surveillance.