I admit that I like the idea of a service cart...my magpie instincts make me want one of those Rat Fink Matco carts.
Here's another idea for tool storage and buying, now that I'm musing out loud.
Besides:
1) Big ol' tool box filled with giant assortment of sizes and styles of fastener unfasteners.
.or.
2) A shelf full of tool rolls, metal cases, and plastic cases with sets of tools...plus a bench drawer full of odds and ends.
I'll suggest another, which I think would be interesting if I were to start over and quit carrying around several decades of accumlated junk on my back.
3) Go to Harbor Freight and buy 2-300 bucks worth of wrenches, sockets, screwdrivers, anything your heart desires. Put in a Rubbermaid box in the corner...
..as you need actually need a tool, rummage through here, use it, and put it in a different box.
...after a year or three, go out and buy either a Snap On or Toolnazi(tm) (Stahlwille/Hazet/Wera/Wiha) brand of the things you actually have used. Go ahead and buy a few variants on those same things (ie. different length sockets, or a wobble socket, whatever....)
If you're me, a crummy weekend hobbyist who owns the same kinds of cars over and over, I'll bet that the entire box of uber-tools would be hand carryable. I'll admit that if I did this for a living at a generalist shop, doing a head gasket for a 1983 turbo Quattro in the morning, a clutch in a V6 minitruck in the afternoon, and sparkplugs in a 1975 V8 Monza right before the closing bell, I'd have one of the 20 foot long 6 axle Matco rigs filled with every conceivable gizmo...of course I'd probably also have a bottle of fine Tequila in the bottom drawer after a day like that.