Goofy fuel systems aren't limited to twin's. Cherokee six has a weird one for some years, any Continental with two tanks you have the fuel return issue which if you don't burn off correctly can cause you to dump fuel over board, Bonanza's with the tank in back have CG issues, Cirrus's are wildly unfun to fly if you get uneven tanks, etc. Then there are twins like the Aerocommanders which have a single tank feeding both engines that is even easier than our Mooney's.
The NTSB statistics on twins are a bit skewed as well. First you don't see all the people that lose engines and don't have an issue only the bad news. Second twins fly a lot more in 135 operations so you have a lot more probability for an incident. I only have one personal experience with somebody killing themselves in a twin and it was the same issue as you see in singles, they got to slow.
The expensive factor for a twin is spot on, the odds of engine loss being greater than a single is spot on, the fuel burn is spot on, the odds of losing an accessory being more is spot on. A twin though overcomes all of the loss factors though by having redundant accessories, fuel tanks, cross feed, and most importantly an engine. Fly fast and life is good! Fly slow and just like in a single you are going to have a bad day but with two more reasons than a single Vmc and Vyse.