Yeah, fence the outside in.
Also, need more exits, since I really can't find many (that isn't suicidal).
Fences will be on the outside (so it'd be seven wide, five accessible, so to say). But this will be for the most popular routes only (namely the loop and a north-south connection). The rest will be 2-3 wide instead without fences, to allow for expansion later if it be needed.
Exits, yes, that is definitely true. Especially in the central area.
I managed to mine 20 stacks of cobblestone earlier today while digging a massive tunnel at layer 40 between my cave base and mega-tower in constuction. They'll go to the latter for the most part, but other than that I'll use them for construction work.
Speaking of massive tunnels, I'm considering complementing overpass with underground accesses too in some areas. Catch with this is that I may run into underground bases by accident (already made another route to someone's 5 x 4 mine shaft in the south by chance).
Found another spider dungeon under the sea too but Kinzo has a string factory already (and we're not even starting on PX's mob grinder). Also I don't think mob spawners are obtainable by breaking them (more barbecues would've been great). and a giant ceiling would be nice but extremely impractical unless I'm THAT desparate for pork and cobble (and water).