Variant in which two pieces can occupy a single square A friend and I tried playing this variant yesterday.  My question is:


  Surely someone has looked at this before.  Does it have a standard name?  Or is there something obviously wrong with it that my friend and I missed?


Sometimes this kind of drastic change to the rules produces a game that is obviously no good.  (Consider the variant in which the board is turned into a torus; White has already lost, or perhaps wins immediately  with 1. QxK, depending on how you look at it.)  This variant didn't seem to have an obvious failure, and we had a good time playing one game and seeing how the tactics differed.

Specifically, the variant we played was:


All pieces move and capture the same as in standard chess, except:
Up to two pieces may occupy the same square.
A piece may move into an occupied square, but not through it.
A piece moving into a square occupied by two pieces of the opposite color may capture either, but not both.
Pieces of opposite colors sharing a square do not threaten one another.


So for example, it was legal for White to open with 1. Rh2, and have the rook and pawn sharing h2.  Having done this they could then continue on the following move with 2. Rh4.  But 1. Rh4 was
illegal.  

Since every chess variant imaginable has been tried out, I expect this one has also.  I'd like to read about it, but I don't know what to search for.
Pierre-Françoys Brousseau found a similar variant on Guy T Shafer's blog “Insane Chess”.   It says:                                                                                                                             


  Crowded chess
  
  Requires standard chess set &amp; board. Pieces setup, and capture as normal.                                                                       
  
  Pieces move as normal, except any 2 non-pawn pieces of the same
  color may share the same square. Men cannot pass through an
  occupied square: pieces are blocked by men as usual. But you may
  pass your own piece in 2 turns (one to move onto the occupied
  square, another to move off that square). Pawns may never share a
  space with any piece.


This is a little different from our variation, in which pieces of opposite colors may share space, and pawns may share space.

Unfortunately there is no real discussion there.