If i were you guys i would convert the old hl1 maps being used in ms:c and use them in hl2. All you guys would need to do is just detail the maps a bit. You could actually use the original models and bring them into zbrush and detail them up there great for a base mesh for a model since there already UV mapped and everything and such low poly. You could actually create some really impressive models by generating a normal map from a high resolution mesh. If you guys did this you could possibly have a internal alpha by mid next year.
-Derek
-Derek