The ability to reference things to an Alignment was the start of this type of request - it really has not been used / implemented fully at this stage.
You cannot share a node between Networks, however when you create the second or third instance of a common Node, you can tag it as Existing so it wont get double counted in a Takeoff / Bid.
Phased Work can cover all the scenarios that you mentioned - whether a Phase is an "Access road" or "Site Development" or truly Phase 1, Phase 2 etc. We have discussed the need to build up phases of work as a part of the Project Definition and this would then allow us to assign eg Utility Runs to a phase from the perspective of "Phased Visualization or Phased Bids or Phased Models" - but that is a bit different to Grouping of Runs within a Network. We did envisage people using Networks to separate Groups of Storm or Sanitary etc type sewers - but we did not accommodate a shared Node concept - however that would likely be the easiest fix here that a Node could be assigned to any number of Networks and only get counted in the "Master Network (first in list or one that is flagged as Master" and in all other Networks it is available but not counted (treated like an Existing Node. Then I think you would get the Grouping that you desire. Phasing can be applied differently because Phase would not necessarily match Groupings in my view
I will log in the request with Product Management.
Alan