Sure but Bitcoin has a bad reputation. Why should anyone with a lot of money from the legitimate world want to hold Bitcoin? Bitcoin isn't stable like gold and is known to drop in value. Also Bitcoin held in vaults get hacked regularly and the developers choose to do nothing to prevent it. This means to most people Bitcoin is basically just a hacker currency.

Bitcoin is now more associated with Mr. Robot than with investments. It's not likely to ever change because once a brand name is damaged it's just gone. I think it's time to move beyond Bitcoin if you're trying to do an ETF and just have a digital currency ETF.