Comments/Ratings for a Single Item

A possible pair of leapers:

Long leaper: same as in this variant except when capturing must jump over
             at least two empty squares before the captured piece.

Short leaper: moves as an Orthodox Queen and captures by overtaking. 
              the piece captured must be within two squares of the
              short leaper. It may land any vacant square somewhere 
              beyond it. It may jumpover friendly pieces, but not 
              capture them. It captures any enemy piece(s) lept over.
              The adjacent square that it lept over must be occupied.
              It may not make more than one short leap in a turn. It 
              may end its move on an edge square only when that is the 
              only way to make a particular capture.

The edge squares are essential for all the pieces since each can be swapped
there, or end there in capturing, if only from another edge square.  The
Long Leaper is a more natural piece than say a Cannon, and 
in Rococo exceeded in value by two other pieces. My estimates:
Immobilizer 10, Advancer 8, LL 7, Swapper 5, Chameleon 4, Withdrawer 3,
Cannon Pawn 2. A Triangulator, as described, or Coordinator for that
matter would not fit in well with this mix of pieces.
CVP has about 2000 games the last time I checked, somewhat fewer than
David Pritchard's Encyclopedia.  Of course, there is substantial overlap,
such as Ultima.

Yes, Rococo and Ultima should both thrive, somewhat as the open standard
and as the closed standard of the same kind of game. That open or closed -
strategic - character derives from the Pincer Pawns in Ultima and from the
edge squares and Cannon Pawns in Rococo.
Where I disagree is about tactics, that is, the officers. I would enrol
one Coordinator, one Swapper, one Withdrawer, one Advancer, one Long
Leaper, one Immobilizer and one Chameleon in both games. I don't see what
makes the Advancer, the Coordinator or the Long Leaper worthwhile only in
Ultima or only in Rococo. Indeed, I find the lack of either frustrating.
(Should one or two new pieces - not pieces capturing by replacement -
prove valuable in a future Ultima-Rococo spin-off, I would also call for
adding them.)
As for evaluation, well, I would reverse George's values for the Advancer
and the Long-Leaper and also for the Swapper and the Chameleon.

Peter, I think your proposal is superior to both the original Rococo and to
what I suggested. The Archer (or the Bird, but I prefer the Archer) brings
in a rifle capture element which is quite overdue. (Should the Archer
prove too strong, I would suggest to have it capture only at a distance of
a Knight's move (or only at a distance of two squares), so as to retain
the possibility of an Archer acting upon an Immobilizer.)
True, Ultima or Rococo probably shouldn't feature a Coordinator if there
are already four officers which capture more or less through relative
position (not to mention the King and the Pawns). However, although the
Coordinator is somewhat arbitrary and sometimes inefficient, it offers a
flavor of delocalized capture which I would like to revive into another
piece, maybe on a bigger board. How about a queen-moving piece which would
capture an officer (maybe not the King) by reaching its starting square.
Or by reaching the square it last occupied?

I've playtested Roccoco with Archers and find it quite playable. The way
an Archer can pick off Pawns is a strength, not a weakness. As in Ultima
and standard Rococo, the Withdrawer is quite weak. Why not replace the
Advancer with the even stronger Pushme-Pullyu and add a new piece type?

Some guesses at Rococo piece 'beginner values':

Immobilizer=4
Long Leaper=3
Advancer=3
Swapper=2
Cameleon=2
Withdrawer=1
Cannon Pawn=1
Archer=2
Pushme-Pullyu=5

Some scary exotics:
LL/PP (can caputure as either or both)=9 
Archer/Advancer=6 
Cameleon/Swapper=5 

Rococo With Different Armies, anyone?

Regarding pieces which simply capture by relative positions, one Advancer
(a Pushme-Pullyu is too strong, and a FIDE-Queen not very different), one
Long-Leaper and one finely-tuned Archer seem enough.

The Swapper, which like the Immobilizer, the Chameleon or the Shield, is a
piece of its own nature, also combines two mechanisms, mutual capture and
mutual displacement, neither of which is very powerful.

Why not have the Withdrawer, which is worth less than half any other
officer, recruit an enemy piece it withdraws from, instead of merely
capturing it, provided that enemy piece has been previously lost?
(variant: it could convert by withdrawing one square, even if that piece
hasn't been captured for its side, and capture if it withdraws two or more
squares)

This raises the problem of Pawn recruitment. Should the Pawns be dealt
with individually, mirror-like, or could a Pawn replace any other Pawn?
I would suggest to make Pawns simply faithful.
(Unmakers require a similar decision.)

Swapper question ... Can a swapper perform 'mutual destruction' with a
friendly piece?  The rules aren't clear on this.

Thanks!

Capture by mutual destruction is capture still, and you may only capture
opposing pieces in Rococo.  The loss of the capturing Swapper is more in
the nature of a cost for that capture.

There is an inconsistency between David's animated illustration for the
Chameleon and Peter's Zillions file.
Is a Chameleon allowed to capture a Long-Leaper and/or a Withdrawer and/or
an Advancer and swap with an enemy Swapper in the same move, as shown on
the animated illustration but not allowed by the zrf?
Besides, is a Chameleon allowed to swap with its own Swapper?
(The zrf allows it, though it is not formally equivalent to the Swapper
swapping with its own Chameleon, since the Swapper may be immobilized.
For the record, a similar rule would be unplayable for a variant with
Chameleons and Shields. The Chameleon and Shield would protect each other,
and the Shield would protect the King.)
If the answer to both questions is yes, is a Chameleon allowed to capture
a Long-Leaper and/or a Withdrawer and/or an Advancer and swap with a
friendly Swapper in the same move?