Using layout-only (physical) instances in Virtuoso XL

Using IC6.1.5-64b.500.8, I have a core design that has a schematic view and when I want to create the physical view, I would like to use a physical-only instance to help create the physical view. This physical-only instance is really a fixed arrangement of pads and wires with no connectivity information but when I connect a net to it at the top-level, I would like Virtuoso XL to recognize that a net should continue to form through these physical-only instances. I guess you can say the physical-only instance is a common template to help wire-up my core design and any other variations of the core design. I expect to tweak this template once in a while if I have to shift some pads or wires for whatever reason.

 The non-ideal solution is to place the physical-only instance and flatten it so when I work on the rest of the layout, Virtuoso XL can recognize the connections I'm making. It won't recognize these connections if I keep it as an instance even after I go to Options->Layout XL->Extraction and set "Extract connectivity level" to sufficiently high level. However, this works if I place a matching pin inside the physical-only instance using the same net name that I expect to use at the top-level, but this may not always be the case. It would be great if it could somehow inherit the net from the top-level when I connect/overlap a wire from the top-level.

 The drawback of the flattening method is that if I want to update the physical-only instance, I need to delete all the flattened elements and re-instance the updated element... then I would have to do this for every design variation that used this physical-only instance.

Furthermore, Virtuoso XL warns me that the physical-only instance has no corresponding element on the schematic and it's right because it's merely just a bunch of wires and pads that will be used as connections. I'd just right click the instance in the Navigator panel and click Add Ignore for Check but I still would like Virtuoso to check if I accidentally made shorts/incomplete nets/etc.

Is there a better way to use physical-only instances when designing the layout of a schematic-based design in Virtuoso XL?