It should be an index fund of the top X coins in terms of market cap, weighted by market cap. Perhaps use coinmarketcap.com to recalculate. I would be happy if X was any number over about 10. Now, this might catch some scams, but it will be self correcting. The primary advantage is the same advantage of index stock funds over actively managed stock funds.
Details tbd include whether the fund rebalances every day or every week or whatever, where to buy the coins that it would hold and where and how to trade to maintain the index-required holding percentages.
Now, cannot say if an index fund is appropriate for crypto market for now, but the concept is definitely what I consider investor oriented.
You can find the Indexes for top 10, 25, 50, and 100 currencies
here. Go ahead check them out.