From this thread and the other on frequency of traded stock, here is something to consider.
The objective of the competitors is to win the competition at year end; the objective of the moderators is to ensure everyone gets a fair shake at winning and that unjustified trades are taken out of the equation as the specific counter may not have sufficient trades.
This is an option to be considered
1) All shares are included on the list of shares one is permitted to purchase/sell
2) Orders to buy/sell are subject to sufficient volumes of the counter being bought/sold having traded on the day. If insufficient volumes then the order is rolled back totally or the buy/sell order is limited to the volumes that went through that day. This infers that the competitor can not buy or sell shares in a low volume counter greater than the shares traded on that day. Thus the buy/sell order would take up the maximum number of shares and the unexecuted volume would revert to cash in the competitors trading account
3) All sales effected are subject to 40% tax and are to be lost in the ether of the sale and this tax is to be taken at the time of the sale. Thus those people who buy and hold their portfolio to the end of the competition would not incur any taxation, but those who buy and sell frequently will suffer capital losses each time they sell. Competitors would then look very carefully at the net result of selling out of a counter either fully or partially.
The competition was set up as an investment competition and not as a trading competition, but it does allow those who want to "trade" to do so it just means the tax will hurt them when they sell more frequently
This is not the only solution but is an option for the competitors to consider and then decide the best way forward