In one of his most recent posts, Der Alte Fritz quotes from a period source that shows the concern Major-General William Forbes Gatacre had for surprise attacks and sudden rushes by the Mahdist forces.
"1. As the strength of a European force lies in the occupation of and in movement over open ground, which gives it advantage of fire, so the strength of a dervish force lies in fighting in depressions of the ground, or in a jungle country out of which they can pour suddenly and quickly their thousands of spear-armed warriors, who, unless checked by a murderous fire, constitute a grave danger, even to a perfectly disciplined force."
"6. That brigades must be so trained that each battalion and individual soldier must know how to get into the best formation with the least possible delay for meeting the attack of the spearmen, who, it must be remembered, can move at least three times as quickly as a British soldier can double."
http://altefritz.blogspot.ca/2016/08/rules-for-engagement-1898-omdurman.htmlIt seems to me that if Gatacre's expectations for the coming campaign are accurately based on the previous campaign, then scenarios where all the Dervish forces are clearly deployed on the table top and move like normal infantry might not be the way to go for some battles.
I'm thinking that something like dead ground markers might be the way to go for a collumn ambush scenario. The terrain is set up and the british column is set up and then estimate where all the dead ground is and put markers there. Until they are scouted out and removed, the Dervish player can deploy from those locations. Perhaps even having one or two "depressions of the ground" counters where they can deploy out of dead ground even without obscuring terrain.
It might also work better to have the dervish player commit to where they have sent out their ambushers so when a counter is scouted or dervishes launch from a certain point, you turn it over and it indicates what is actually there.
Could make for a tense game.