I recently handled this by making a Design Option Set for Topography, then for each Stage / Building Option combination, I added the entire site Toposurface. From here, I could use model groups to transfer pads between the different options / phases, while still retaining their size and position and editability. It was a pain to set up, but once configured properly (with views etc), it seems to work ok.
The most 'logical' way to configure it would be:
- Make a Design Option Set
- Make an Option called 'Existing'. Add your original / untouched site topography here.
- Duplicate the Option, call it Stage 1.
- Make all the Stage 1 pads, then group them.
- Duplicate Stage 1 topography option, call it stage 2 (the grouped pads will come through). Add additional pads in Stage 2 option, then group Stage 2 pads and the Stage 1 pad group (forming a nested group.)
- Rinse and repeat
You can read about the problem at:
Re: Building pads don't seem to respect phases. - Autodesk Discussion Groups