There are technical limitations too; a long time ago I was working on a WWI game based on the q2 engine. The problems are more or less that no man's land is a large, open expanse with a lot of detailed terraining for craters, etc, and shattered tree stumps, and this engine would just choke on it completely. You'd have to go with really dumb angular terrain to keep wpoly down, and that's even without cool pools of reflective muddy water in the craters.