that not a good idea in conventional chess but good in variation chess game.
however I think the rule of chess in pawn promotion on "bigshop and castle "should change a bit,I feel it quite waste idea since we always promote on queen..which have the both ability.
This is also the argument I heard yesterday. I suppose it makes sense but I like the actual rule MUCH BETTER! ...
I found this rule at FIDE.com. From E.I.01A of the FIDE Handbook, Article 3 of the Basic Rules of Play, 3.7.5 states "When a pawn reaches the rank furthest from its starting position it must be exchanged as part of the same move for a new queen, rook, bishop or knight of the same colour. The player`s choice is not restricted to pieces that have been captured previously. This exchange of a pawn for another piece is called `promotion` and the effect of the new piece is immediate."