[baronspam]

IMHO the street level/prime runner rules in the character creation chapter don't work that well, as they basically modify starting resources and gear.  The hurts/helps characters that rely on alot of gear for their build, but it doesn't do much for magical characters (other than make focuses harder/easier to get).  I would suggest using the street scum/high life options in the GM's chapter if you want to change starting power level, as they change the priority options used to build characters, thus impacting all types of builds more evenly. 

[Belker]

I think when the OP used the term "Missions", he really meant "Adventures", rather than specifically the episodic "Missions" living campaign.

Explanation for the OP: in Shadowrun, "Missions" specifically refers to short, fairly self-contained adventures which are intended to be played in single 4-hour sessions at conventions or as game store events. There are a number that are completely stand alone and take place anywhere in the world; others are done as small groups of 3 or 4 linked adventures; and as part of "Seasons" which consist of a large number (10 or more) adventures set a particular city such as Seattle or Chicago, with several interlocking story arcs.

It really sounds like what you're asking for are more generic "adventures", which can take any form.