Whisk together vinegar and mustard in small bowl. Slowly whisk in oil until emulsified and thickened. Whisk in water, then shallot; salt and pepper to taste, for vinaigrette.
Bring large saucepan of water to boil; add salt. Add beans and cook, stirring occasionally until just tender, about 3 minutes. Transfer to a bowl filled with ice and cold water, reserving water in pan. Add shrimp to boiling water and cook until pink and opaque, about 3 minutes. Transfer to ice bath. Drain beans and shrimp; pat both dry.
Place potatoes in clean saucepan. Cover with cold water by 2 inches and bring to boil; add salt. Simmer until potatoes are tender but not falling apart, about 15 minutes. Drain and rinse with cold water; halve. Separately arrange beans, shrimp, potatoes and lettuce on large serving plate. Peel and quarter eggs. Tuck into lettuce for presentation.
Drizzle vinaigrette over all. Salt and pepper to taste. Serve with warm bread if desired.