If all you want to do is increase the texture resolution, just keep the proportions the same and use a uvmapper or a 3dpaint program in whatever resolution you want(bearing in mind any memory restrictions.) But I see from your second post this isn't what you want to do. Sounds like you'll have to make a whole new HI-RES character to increase the mesh size. Nightmares of the heirachy editor still haunt me when I tried that. (But then I didn't know about Renderosity at that time.) Guess that's why DAZ is so popular