Vitya, I have played against my Circular Chess program and I can tell you
that it seems to works fine without the 'en passant' rule. One cannot
easily create a pawn blockade anyway. In Circular Chess the pieces have
different values. Firstly, the rook is more valuable, probably it's worth
more than two light pieces. The light pieces seem to be worth less than
three pawns. Probably a light piece can, at times, be exchanged for two
pawns. This means that a pawn blockade can often be removed by exchanging
a piece for two pawns. The situation on the circular board is more
unstable than on the standard board, and there is no sufficient hideaway
for the king. I don't think you have to worry about cowardly drawish
play, using pawn blockades. After all, reasonably strong players have
tested this variant in the yearly Lincoln tournament. It works.
/Mats