Wouldn't the surplus value be accounted for in the form of having more good in your inventory? The bigger issue IMHO is that goods require *only* labour and when used disappear into nowhere with absolutely zero effect apart from shuffling some money around. It doesn't matter whether you give your people 100 cars or 10, they'll be equally happy as long as the minimum amount is reached. This is obviously not the case IRL. Surplus value in the form of excess goods just sits there and does absolutely nothing. Productive forces are not simulated, allowing you to ramp production skyhigh at zero cost.
So, I suggest a solution: an expected standard of living, factories, and foreign trade.
There is now an expected standard of living, which is a function of the different good demands. Demand per labourer for a good starts small, but grows up to a certain point, faster if it is fullfilled. If demand is 100% fullfilled for some time,it actually decreases a bit (to simulate people stopping hoarding it. Also means that during shortages it can suddenly jump up).Therefore people will get mad over a lack of pocket watches if they are used to them (high demand) but not if they are a novelty.
The actual living standard is how much a labourer can afford, which is usually not enough to satisfy all of the demand (expensive stuff doesn't have to be bought whole. Gotta save up for that Trabant) If it is, labour savings appear and demand rises much faster.
Unrest is no longer directly tied to shortages, but to a big mismatch of expected and actual living standard.(small mismatch is fine.) Exceeding the expected standard should have bonuses-slower rate of demand increase maybe? Or possibly higher population growth.
To produce something, you now need to spend resources to build up factories for that first. Resources are a type of good that can be produced, but can't be sold to the populace.
There is also a counter for how much foreign currency you own- that can be increased by selling goods abroad and can be used to fullfill shortages of goods or resources.
Overall this gives the choice between making an export economy and just buying consumer goods from abroad, industrialising to bring long-term benefit at the cost of short term bad living standard, or going after consumer goods and increasing the living standard.Research should ideally depend on your living standard and light sector, as intensive growth is what planned economies historically struggled with due to overfixation on heavy industry.
Another suggestion would be adding a MIC, which is for all means and purposes an unproductive money hole that if ignored could lead to an invasion and game over.Maybe have it give a small research bonus tho.
I have no clue why I just wrote all that, it's late and I want to sleep. But yeah, THOUGHTS?