I'm a bit leery of keeping the group in one location and of making that location static. The more you go to any one safehouse, the less safe it is. People will notice you, friends will know where to find you, your datatrail will show repeated use in the area, and if you go there and stay there as a group it'll be easier to identify. At that point, your safehouse is little better than a plain old house. You can arm and armor it as much as you want, but siege tools/tactics tend to win out.
In my opinion then, a good safehouse should be used only once, preferably by only one person. The fewer people that know, the better ("three can keep a secret if two are dead" and that sort of thing). There are too many potential boltholes out there to bother with keeping any one of them.