You should consider making an actual composite index before the ETF. SPDRS did not come before the S&P 500.
Some questions.
Will all assets on GLBSE be listed and held based on their market capitalization?
If not all of them, how will they be selected to be included in the ETF?
How will you determine, "Only GLBSE assets with outstanding shares are eligible for inclusion."? Will you look only at assets that have an ask? If this is the case, should you instead use an available market capitalization instead of a total market capitalization?
Will you hold bonds?
I made the index first and have told people about it. So far, the only thing anyone has expressed a desire to be published about it has been a list of included tickers.
Nearly all assets on GLBSE will be listed and held according to their market cap relative to each other. Some things are not included because it would misrepresent the status of GLBSE. A good example of this is other ETFs or assets which only hold other GLBSE assets. They cause an 'exaggeration' of the market if they are included in the index.
I requested and received a custom api call from GLBSE which returns the number of outstanding shares. The order book does not affect an assets weight in the index.
The index does list bonds, so the ETF will hold these bonds when appropriate.
As an example of how 'the big boys' do it, this is the methodology of the iShares NYC which tracks the NYSE composite index:
Methodology. Only common stocks, ADRs, REITs and tracking stocks listed on the NYSE are eligible for inclusion in the
Underlying Index. Multiple classes of shares of the same issuer are eligible to be included in the Underlying Index. Preferred
stocks, closed-end funds, ETFs, trust units, shares of beneficial interest, shares in limited partnerships, and derivative
securities (such as warrants and rights) are not eligible for inclusion in the Underlying Index.
