my 2p
You can go bananas and carry all the stock from a resus bay but to be honest theres not much point, assuming you are in the UK you are lucky enough to be (usually) within a short time/distance of help. You run the risk of fighting an exponentially increasing equipment list, i.e. theres no point having IV access devices if you then don't carry fluids/drugs/giving sets etc...
FWIW I'm a doctor, who has trained in A&E, and is a advanced trauma and life support provider, I carry the standard first aid kit that came with my car, a variety of guedels, a pocket mask, and make sure my phone is always charged....
I would of course take more stuff with me if I was off into the middle of nowhere...
As with all these things making sure your training is refreshed regularly is more important than the equipment.
Mike (bored sitting waiting for my bleep to go off!)