Well since I spend too much time thinking here are my thoughts. I can of course be wrong as I'm really just guessing.
1) What will be the effect on goods in shops - will they just stop being delivered or will they become more expensive. If so which goods?
I think both will happen Anything that isn't coming from next door right now will get more expensive. Some things just won't be available.
Anything that doesn't need to be preserved (coffee, tea...) will still be available it may just take much longer to get, will be rarer and will cost a lot more. Anything that has to be rushed somewhere before it spoils will not be available or will be ultra expensive. I expect to never eat another banana shortly after it hits.
True luxury things will be less available. Can you imagine paying to ship cotton from egypt for sheets when it's available in the southern US?
2) Pensions, loans, mortgages, other 'on paper' investments. What happens to them if there is an economic depression? Do the loans get defaulted or do the banks become heavies?
Pensions are already questionable in some industries namely the airlines. I have zero faith that I will ever see a penny of mine. Loans are almost always made on collateral of some sort or for something of value, I bet if you can't pay they come to get it at least at first, after 90% have defaulted I don't know if they will bother trying to collect or if it will all just vanish. Mortgages have value because of the land they are on. This is the one that concerns me. The possibilities are basically They forget the debt when everyone defaults or they take the land back. If they take the land they may possibly make you work to stay on it while they own it, and we're back to being serfs. Thats pretty doomer but is a possibility. Other paper investments are likely to be worthless in my mind.
3) Do we think the current economic system will work or will we need to revert to local trade, different currencies, rationing?
The current economic system is propped up in lots of places as is, I have no faith it will survive. Local trade will be necessary even if the current system survives, it just won't be worthwhile to ship items 1000's of miles. paying someone $2/ to make a $40 item instead of paying someone $15/hour to make the same item makes no sense if it costs $30 to ship the item from the $2 guy to the customer but only $10 to ship from the $15 guy to the customer. Free trade and exporting the manufacturing sector will bite us on the ass.
Long term I see different currencies in large countries like canada and the US simply because they are too spread to stay stable without easy transport. In the short term (my lifetime) I expect to see them stay together and use the same currencies as they currently do.
Rationing- almost guaranteed in some places, but there will be a glut in others. Eventually things will balance.
4) Jobs, careers - which sectors will be hit first, and which ones will be worst affected?
I strongly believe that transport and anything involved in transport will be the first hit. Airlines, truckers get beat up by the costs, then they pass it on to the suppliers and they get beat up. IN the end I figure only farmer and soldier are safe jobs. Everything else is pretty much a luxury. I make software that does the equivalent of push paper for an industry that relies on big trucks full of trees hauling logs 100's if not 1000's of miles to be cut and then halued somewhere else to build with, I won't be reaching retirement age doing that
5) Where will government resources be placed? Which sectors will lose out?
Where will they be placed and where should they be placed I believe are different things.
I expect subsidies to keep trucks and planes running, the money should be building more trains and railway lines. I expect oil and coal to complain that it's too expensive to hunt for more so subsidize us. At this point Nuclear should be building full tilt just to keep up with demand. I think it's too late to make renewables usefull in all but specialized areas. Eventually they will be the majority, but we'll be doing far less then.
Sectors that lose out. Education would be easy to chop even though it's a death blow for any form of future. Military goes strong at first but will eventually be cut back dramatically. 1,000,000 soldiers don't mean crap if you need to load them on sailing ships to get them there, just ask the chinese. Research in anything non energy related will probably be cut way back. No need to cure cancer if they are starving and in the dark to begin with.
Anyways thats just my guess. I'm a doomer but I don't expect a mad max crash so much as a slowdown that goes into serious and unending depression mode.