If the walkover player has already inform the organiser well before he entered TOP8 and the organiser has no objection at that point, then his ranking should remain. If he satisfied the promotion rule then he should be promoted to Grade B player status.. In the case of too many walkovers, then it is up to the orgainsers to hold emergency meetings to handle the issues.
[2] Prize money
However, to maintain the integrity of TOP8, the Rank 9 player is promoted to ensure there is no walkover. His prize money is given to the walkover player and also has the chance to fight for the top prizes sa one of the TOP8. The same applies for other walkover players. In the event he can achieve 3rd or better position, he will assume that position and prize money and be promoted to Grade B player status.
All rules should try to be fair and reasonable to all players involved unless the rules are already stated before the tournament. The main key idea is to keep the interest on CHIchess going.