How do you plan to store it?
Gold and silver stable coins are much to be backed by and audited as there are many ETFs around. Those coins are like a crypto paper gold backed.

There are no diamond etfs. I don't think you plan storing your coins back up in your house.

Why do you think some investor would sponsor your project? Shouldn't you try to go to big diamond holders(like etf admins, such as sprott) and present your project to them?

It is much more interesting for an investor to buy a diamond directly and cut off you, the intermediary

https://www.thewealthadvisor.com/article/diamond-etf-gem-trading-opportunity