The consensual fight by definition is not a "gank". Which also seems to be one of the core problems here: you don't seem to use the term "gank" as what it means: attacking a weaker target, looking for an easy kill.
Fair enough - though as we've spoken about previously in this thread, figuring out exactly what constitutes a weaker target is not always that easy to define.
Once you've finished scanning somebody, you can see what their ship build consists of - but you can't tell if it's engineered or not. You can tell from their combat rank how much combat experience they have - but we can and do run into the alts of
extremely experienced players on one of their "smurf" accounts. Likewise, we've established that being in an "endgame" ship like an Anaconda or Corvette or Cutter is not the same thing as having an endgame build (engineered shields, etc). Again, hard if not impossible to know for sure until you fight them.
It would be possible to come up with a complex RoE to try to account for these things and be a "nice ganker," but again - the validity of the target by these pretty amorphous, hard to pin down standards is always going to be subject to the "Why?" reaction, regardless of how carefully you try to define your criteria.
So, one rational solution - just interdict everyone you see. That has the added advantage of giving you the maximum amount of "emergent" gametime possible. And then send a friend request afterwards. If they accept, you can have a chat, maybe share some tips, or even - as
very often happens for me - get a legit 1v1 with them, in a combat ship that
they choose. This allows your 'victim' to have revenge - always nice - and gives you, the ganker, more PVP. This is a win/win in my book.