You *can* create single phase panels:
240 V Single Phase Panel Family
1. Open 208V MCB Lighting and Appliance Panelboard - Surface.rfa.
2. Select the connector, and select Properties.
3. Make the following settings:
a. Number of Poles = 2
b. Voltage = 240
4. Click OK to close the Element Properties window.
5. Save the file as 240V MCB Lighting and Appliance Panelboard - Surface.rfa
As far as plumbing content... you could 'harvest' this content from the architectural models you are working with, or even from the tutorial files... but this will be mostly for display only, as you indicate, there is no support for sizing based on FU.
As you found, Revit Systems is a modeling tool, not a drafting tool - since schematics are not modeled elements, you will be more productive using an AutoCAD based product for those tasks.
HTH,
Martin Schmid
Autodesk Consulting
Martin Schmid
Product Line Manager
Mechanical Detailing and Electrical Design
Architecture, Engineering, and Construction
Autodesk, Inc.