Succession planting

Last week I visited the Chicago Botanic Garden for the first time and their vegetable and herb gardens were beautiful. I was struck by the perfect spacing of broccoli, chard, lettuce and other greens, and noticed that everything had been transplanted from cold frames. The lack of bare spots got me thinking about starting more things - even warm weather vegetables - in flats so that each spot in my garden might be filled with a healthy plant. I think it would be nice if I could plant a row of beans from a flat and have no bare spaces. I always direct-sow my beans in the row where they're going to grow, and I don't always re-seed bare spots because by the time a row is growing I don't think a two-week laggard will contribute much.
I do a good job starting tomatoes in my basement when the ground is cold and shovels are still by the door. But once the growing season starts, I tend to wait until a space is vacated before I sow anything new. My wife doesn't like seeing bare dirt in the garden; she thinks something should be growing there. So, with about two weeks before my arugula bolts, I decided to start a few things in flats and be ready when my lush rows of arugula turn to bitter, woody stems. Perhaps I can shorten the time before the next thing is ready to eat. So this evening, after I put the kids to bed, and just before this now-falling rain began, I filled two flats with beets, kale, cucumbers and beans.
I've never started beans in a flat and have heard they don't do well as transplants. Well, we'll see. Just as I don't mind losing a row or two of a too-early planted spinach or lettuce, it'll be good to learn if I can transplant beans. More than anything, I think the flats can be a good idea because it's easy to control the moisture for the germinating seeds. Until then, it's still arugula for lunch!