I think that it is generally true that any "all-purpose" tool is less-than-ideal for most purposes. There are trade-offs for everything.
If you are just looking for a bike that allows you to ride fast and long while carrying a load, though, I think you are looking for a light touring bike. Get something with drop-bars and road-y geometry. Get a comfortable saddle for it--maybe Brooks B17. It will go reasonably fast (not racing-bike fast, but certainly faster than my Globe Vienna).
Personally, I am not following my own advice--I am doing what you suggest on a mid-80's Schwinn steel road bike. I have racks and fenders on it. It goes not-as-fast as my racing bike but fast enough for sure. When I routinely carry lots of heavy loads on it, I start breaking spokes but that's the wheel's fault and not the frame. The old steel Schwinns really do never break--if you put the right components on them, they will haul anything you want.
At some point I may replace the Schwinn with something more modern. After all, I'm running it with old 105 gear and down-tube shifters. Generally fine, but when I can afford it I'll upgrade. My Vienna has started to spoil me, with its IGH and shiny paint.
In your position, I might consider a Civia Bryant. Go with the belt-drive option. It can haul a load, go fast, seems comfortable (having only looked at the geometry), and is low-maintenance.