PTC_CONSTRAINTS_SET in simplified rep

From your description, I think using flexibility may be what you want to use.  Simplified reps get unwieldy when using them in assemblies and sub-assemblies.  You can do a lot with flexibility, including suppressing and unsuppressing features and components, changing dimensions, and controlling constraint sets.  Below are my notes for varying constraint sets with flexibility.

USING CONSTRAINT SETS FOR ALTERNATE ASSEMBLY LOCATIONS 

• This method creates multiple positions for a part in an assembly, such as placing a bolt in different bolt holes or lining a part up to different bolt holes.  Dimensions can also be varied using flexibility along with this method, See the following link for detailed description. 
• How-to-Make-Multiple-Assembly-Positions 
• Create multiple constraint sets 

Constrain part in first desired position. 

• Disable Constraint Set 
• Select New Set at bottom of Constraint list 
• Repeat for all needed positions 
• Rename constraint sets to something meaningful 
• Activate desired default Constraint Set 

Refer to FLEXIBITY below to add pre-determined flexibility. 

• While adding predetermined flexibility select the Parameters tab then plus sign 
• Change Filter By to “Current and all sub features” 
• Select Component “xxxxx.asm” / PTC_CONSTRAINT_SET then insert selected and Close 
• Select OK and close Model Properties 
• When adding model to assembly, choose parameters tab in flexibility and enter desired Constraint Set name.

FLEXIBILITY 

• Predefine flexibility in a component or assembly go to File / Prepare / Model Properties. Select “change” for Flexible under Tools section. 

When part or assembly is assembled into an assembly you will be prompted to use predefined flexibility. 

• Select a feature or part to flex, select dimension to vary, and select OK. 

• Repeat for additional feature or part flexibilities. 
• Select OK.