I have seen what you think as bad actually work. I bunch of sites is only worthwhile if they each have there own independent non paid for old backlinks. Ditch any sites that only have links from your network. They are completely worthless. There is no problem for them to be on the same subnet. I would give them their own IP because that is really easy to do an not expensive. There is no problem having the same whois info. You are going to be spending a lot of time and effort for something that has no real value. You will not see any improvement by doing what you say. You will still need to go out and do other SEO work for them to be happy with your work unless they are hiring you specifically to do this and they don't care if it works or not. If they want it done on your recommendation don't do it. I have experience in this area and I know what I am talking about. There are tons of things that your time can be better spent to improve your ranking. Any site that has their own backlinks have them all point to one main site and get it's PR up. This will take a while. Any kind of linking strat takes a while nowdays. Also you need to tell them that being the top 25 is the best way to get knocked out completly.