I love doing projects like this. Generally, when I do them, I try to minimize my out-of-pocket cost by using, as much as possible, stuff that I already have on hand.

I'd be for trying just the middle chainring on a triple crank and bottom bracket. That should yield a straight chainline with the middle of the cassette. I'm thinking that chainline is going to be important or, with no front derailleur, you might derail the chainring when you're in either extreme cassette cog.

If you want to go for a "different look" there are a gazillion handlebars with different bends. They'll drove your choice of shifters and brake levers because some are designed for road components and some for flat bar components.