Currently we are using a very high level (customized) and mature formal re-use methodology in BoardStation.
Right now I’m doing some investigation about (in-)formal reuse in Expedition Enterprise. I’m facing the same problems you’ve mentioned in your post.
These are some of my findings:
Constraints defined in the reuse block are not always maintained once the reuse block is instantiated from the central library. Checking the reuse block in the library is ok, once instantiated, even in a new design, all constraint values are set to 0,254 and some nets even have lost their constraint value. This looks like a bug to me.
Connecting a reuse block merges the traces, due to this it’s impossible to move (re-locate) the reuse block. This looks like a bug to me. According Mentor this should be solved from EE2007.5, however this exactly the version I’m running on.
Up till now I couldn’t find a way of working to upgrade a reuse block, maintaining the rest of the design. Suppose you’re changing a design, containing several reuse blocks, and one of them needs to be updated (schematic and layout).
There is no lifecycle management for a reuse block, in other words no possibility (unless manually organized by means of properties) to find out from which board the block originally was created from.
for sure there are still other issues, tips and tricks, that's why I agree on your statement it would be a good idea to start a forum w.r.t. formal and informal reuse.