Somebody needs to develop a legitimate, serious altcoin index and an associated index fund!
Couple of years ago, I started doing it. I have some ideas about re-balancing (kind of a big deal, has to be done far more often than the re-balance S&P 500, for example) and cap-weighting versus price-weighting. I just don't have the technical skillz to pull together the proper APIs and such.
It would be interesting to see how such an index would fare (mostly not well, I fear) and also I think there would be some demand for an index fund or an ETF-style basket of alts.