A take-with-you ditch bag is a great idea and habit - as searun outlined above (always appreciate your posts and insights, searun!).
For me - I keep a few simple tools (screwdriver with bits, 2 adjustables, knife, etc.), file/sandpaper, couple clamps, assortment of fuses (they take practicably no room nor weight), waterproof flashlight, waterproof hand-held VHF, small GPS loaded w charts & tracks, smallest package of flares w pengun, extra AA batteries for units, and 1st Aid kit. It all fits in something less than the size of of a backpack - about the size of 1 grocery bag but in a waterproof bag. Easy-peasy to take with you no matter which boat you go in. Should handle the vast majorities of minor "emergencies" before they get to be an actual emergency...