I agree with Voigtkampf and Dead Moroz - one of the biggest reasons for RTW being less challenging than STW and MTW it is that it is less common to find yourself outnumbered on the battlefield. Whereas this was almost the norm in MTW and STW. Pumping up the AIs resources - by playing on very hard or by EBs scripting - may guarantee you face full stacks, but you rarely get hit by multiple full stacks.

I agree that some kind of "march to the sound of the guns" reaction move system could help offset this (effectively widening the circle for which stacks fight), as would programming the AI to gather, move and fight in contiguous "hordes" of full stacks, rather than treat each stack independently. BI made some progress in terms of the latter, although there was still a tendency to let hordes be salami sliced to defeat.