Hello all,
So, to address the various points:
Framerates
The city areas will actually have (as pointed out by various people) rather good frame rates - because I make new objects that are large blocks of buildings, a large dense appearance can be achieved without many objects. So, despite the fact that the city looks really dense, it isn't actually that many objects. I anticipate final frame rates will still be really good.
Timeframe
I am aiming the map to be a WW2 map, but the default building status will be intact. The city ground texture will be tweaked to be a little less tidy and green, but I think that using the Destruction brush is the way to go. Remember you can destroy the entire city in a few clicks. The new blocks I've made have their own destruction models. Whilst they aren't as detailed as the ones from TOW, remember I'm aiming to have a huge populated city with great framerates. Replacing the buildings with objects that are more numerous and more resource-demanding will be counter-productive. The default Reichstag and Brandenburg gate objects (that have no damage model) aren't going to be used - they're the wrong scale. I'm going to be making new custom Berlin landmarks/buildings.
Joe