I've just added things over the last few years that I needed or planned on needing. For Skidoos the most common wrenches needed are 10mm and 13mm. So I carry those two in gear wrenches, and a few box wrench socket adapters, which turn the two wrenches into a 1/4" drive ratchet or 3/8" ratchet to work with my small socket set, and there's an adapter for bits. Also a 1/4" ratcheting driver, 6" magnetic extension, and adapter for numerous bits (hex, star, screwdriver, etc), and socket adapter. Also homemade spring puller, wire, duct tape, electrical tape, common bolts and nuts, steel epoxy, extendable magnet, small pair of pliers, leatherman, knife, zip ties, hose clamps, some other stuff I can't remember...... I wrap duct tape around a pill bottle, and fill the bottle with the nuts and bolts.
And it all fits in a makeup bag that takes up less than 1/4 of my pelican case. And I do use them a LOT so I'm always working on keeping the essentials and finding multi purpose tools to keep weight down- like the box wrench adapters- really nice! Or just a stubby ratchet- those are great for tight spots. Check out Harbor Freight. I know some of their stuff is cheap, but it's affordable and for the most part decent tools for a kit- I haven't broken any of them yet. Not Snap-On quality, but we can't all afford a full Snap-On tool set.