Title pretty much says it all. I know we have approximately eleventy-bajillion lawyers. We also have doctors, scientists, engineers, cooks, writers, mechanics, pilots, soldiers, sailors, gun guys, etc. Seems like for just about any topic that comes up, there’s at least one Doper who would probably qualify as an expert witness in the field…or close to it. Do we have all the bases covered? Are we missing any major area of expertise?
Stranger on a Train would certainly fill in any gaps. 
What about athletes? I know we have sports fans, and our understanding of baseball statistics rivals Nate Silver’s. We clearly can play video games and participate in fantasy leagues. But do we have people who really play the game (other than running or cycling?)
We have some who claim proficiency in various martial arts but I don’t know if any compete.
I dunno about professional athletes, but we have plenty of people that played varsity sports in high school, and probably some who played at the college level as well. Also pretty sure we have people that play golf/tennis/swim regularly. Probably have some that play recreational soccer/softball/basketball and/or participate in martial arts. We’ve got one well known poster who played rugby until suffering a horrific injury. His mother logs in occasionally to update us on his progress.
Most are certainly replete.
Medieval Ethiopian sewage technology?
Ethiopian sewage technology is by definition medieval.
Scratch out hole. Poop into hole. Cover hole.
Next question?
Check with Dung Beetle. 
I don’t believe that we have any optimization experts on the boards, although I’d be glad to be proven wrong.
I know we’ve had some posters who’ve run for office but do we have anyone who’s holding elective office?
Nemo: Keep tabs on Jonathan Chance, I think he’s in the running in his election.
I think SpoilerVirgin got the key shortage. I can’t recall OTTOMH any Dopers who have been professional athletes in the US major leagues (NFL, NBA, NHL, NL/AL).
Dio’s an expert on everything.
I wouldn’t be surprised if Tamerlane might not have done a dissertation on it.
Do we have any experts on eschewing obfuscation?
Optimizing what? I did a lot of work on optimizing operating systems in the late '70s.
If local offices count, I’m sure I’ve seen a number of councilmembers and such. My wife was a school board chair.
That’s what I do for a living.
Do we have any merchant seamen here? Commercial fishermen? Roughnecks? Miners?
Lots of skilled blue collar jobs seem lacking.
There’s probably a shortage of practicing Amish folk in here.
Well, blue-collar workers would tend not to post to a board like this one. However, it may be that some of us spent part of our lives in blue-collar jobs. I once worked for 6 months in a steel mill, the first 3 months as a cleaner, and the second 3 months as a Brinell tester (an occupation that I had not even heard of before I started doing the work).