My MKIII Octavia has a strap for a fire extinguisher... although it is located at the very rear of the boot which would seem like the most dangerous location to me but I guess VAG know what they're doing.
I don't think there's any great advantage to lugging workshop tools around. If you can't change a wheel using OEM supplied equipment you might benefit from some formal driving instruction or you may be better suited to a non-driving role. I am the proud owner of a brace of trolley jacks and a bottle jack, all of which reside in my shed but if I were inclined to carry one in the car I reckon the bottle (cheap 4 ton from Halfords) would be the best fit, in fact the foam in the spare wheel well could probably be modified to safely accommodate it.