Pathfinder is also turnbased -> yet P:Km and WotR are RTwP.
Something I haven't seen mentioned (apologies if I missed it) is that P:Km began as a RTwP game; TB was only added later. I'm not sure how much more difficult it'd be to add a RTwP mode onto TB game, but I could imagine it being more difficult.
I bet it would be more difficult. The AI itself would probably have to be rewritten as it would be moderately playable with the current one. In the case of RTWP, AI has to be relatively stupid for the player to have any chance.
Even with pathfinder how it works. The AI in the game is downright dumb, instead the opponents have extremely high stats. Blackwater before nerfs is probably one of the best-known examples.
