Of course all manner of obnoxious dealings occur in capitalist and coordinator economies. In a participatory economy one can't cheat to get rich or even to escape work, except maybe by faking illness. Remember, it's your neighbors and workmates you'd have to fool. Not a boss on a cruise in the Caribbean or a planner 3,000 miles away. Given that each person winds up with a roughly average set of burdens and benefits, the real issue is having a say in what that average will be, deciding whether to borrow or loan, and determining the particular components of one's own work and consumption.
Misrepresentation is self-defeating.
There is something to what you say-in fact, examining it without prejudice, all you've done is replace markets with a primitive barter system. But we're not talking about establishing a system to work on some tiny island or for a group of friends going on a two-month outing. It doesn't mean much that you've overcome difficult problems present in realistic models by proposing an alternative only applicable to tiny economies where everyone can know everything. Hard as it may be to believe, moving and managing information, summarizing it, averaging it, and otherwise shaping it into useful formats that people can relate to won't be a big deal. And regarding assessing purchases in advance, actually much of what is produced in modem economies is bought by companies and other institutions that already pass judgment on alternative possibilities well in advance, as, for example, when General Motors estimates car production and puts in orders for rubber, steel, etc.