Say you take x shares and turn them into a cryptoUSD. Now you have a cryptoUSD backed by the discounted present value of txn fee revenue from x shares.
Say you take x shares and hold them. Now you have x shares backed by the discounted present value of txn fee revenue from x shares.
Ignoring liquidity issues, the value of the cryptoUSD should remain constant when denominated in shares. The USD value of a cryptoUSD will go up and down, just like the USD value of a share will go up and down.
You're going to tell me that the cryptoUSD will go up and down in share-denominated price, etc., etc. Why? Suppose it doesn't? Isn't that an equilibrium?
You need to a) create an incentive scheme (e.g. reward issuers that create frequently transferred assets) or b) peg your derivatives to something with a physical interpretation (e.g. PoW difficulty).
I suggest you save your money for a well thought out project.
You overlooked the critical ingredient that makes this work.
1) when the crypto-USD is created, it is actually created slightly above market value. New crypto-USD can only be created when there is no one willing to sell existing crypto-USD at the current crypto-USD to BitShare exchange rate.
2) all crypto-USD is fungible. So if you only look at 1 transaction, then what you say is true. But if the price changes between crypto-USD then the 2nd, 3rd, and 4th depositors will demand more and more BitShares to back the new issuance of crypto-USD such that when each of them receives their crypto-USD in exchange for paper-USD then it would be near parity. Otherwise they wouldn't buy crypto-USD they would just buy BitShares directly. The reason they buy crypto-USD instead of bitshares is because they know everyone else who also WANTS a USD denominated crypto-currency will demand that it have near price parity before they would give up paper-USD for crypto-USD.
3) If crypto-USD failed to maintain parity with actual paper-USD then there would be no depositors. Therefore each and every depositor represents a market force that corrects the ratio of dividends between BitShares and crypto-USD.