Blueside, contacts in a given level range will refer you to others within the same level range until you have a full set, and you can meet others via detective after running a safeguard mission (although this seems twitchy sometimes), so it's impossible to get "blocked off" from a certain chain.
Back on live I had a scrapper whose goal was to do every blueside mission in the game. I had gotten pretty lucky; I got through the "go hunt in Dark Astoria"s before Mot ate it, and if the game hadn't gotten shut down, I would have probably finished it all up before Kings Row became the first new content added below her level. Here, I'm going for the relatively sane "all story arcs, all badge missions, maxed contact bars" on my main, who will hit 40 tonight. Ten levels to go...