-Generator variant, called "Matrix" ?
-Peces on first rank never move but generate new pieces. Pawn don't generate.
-A generator captured and replaced by a similar piece does not generate.
-King does not generate. No castling. En passant possible?
-Goal is still checkmate.
+Would be nice to display some better variants names (Pacosako -> Paco-Ŝako etc),
+but the "formatted" name with uppercase + all lower cases would still be required.
+(For example in variants list, or tournament variant field).