If the odds that BTSX has a serious issue/failure in the next year are 2% then a BitAsset is only worth 0.98 to a long term BitAsset holder.
A genuine BitAsset holder also has to consider the utility of a BitAsset or the cost of conversion to acquire the real world counterpart his BitAsset mirrors.
So even if your proposal resulted in a tighter range than the current few % now it wouldn't attract genuine buyers because a BiAsset isn't worth 1-1 in the medium term because of risk, conversion & utility costs which is why you have a dead buy side of the order book.
Interest will offset these factors and does make BitAssets 1-1 or better which attracts buyers at 1-1 Therefore making a bigger market than the current one and it creates the peg at 1-1 (because the interest applied in this way is self-regulating.)
Empirical, you are making a PERSONAL value judgment here. Just because a bitAsset isn't worth 1-1 to YOU doesn't mean it isn't worth 1-1 to somebody else. There are still advantages to bitAssets and as long as it is worth at least 1-1 to somebody then we have demand. The trick to the peg is we adjust supply to whatever the demand may be. So if we make bitAssets more attractive and useful than we can sustain a larger supply/market cap for the bitAssets: It affects the total supply rather than changing the peg. The mechanics of maintaining the peg are more dependent on the shorting/covering rules.
I don't think it's a personal value judgement to say at the very least current demand for BitAssets is not matched with current demand from people looking to short and that people looking to short are willing to pay a premium to incentivise customers for their short.
While I can see your strategy matches supply with current demand as you say - and in that sense it works - it's just a very small market because current demand is so low.
You're also strangling & suffocating the market because the shorts are willing to pay to a premium to attract/incentivise buyers & in so doing create a much bigger market of buyers and sellers. It's like trying to stop a store from offering incentives to attract more customers, if the store is willing to do that let them. Don't let them sit with $2000 leather jackets on the shelves with no customers when they want to sell them for and can still make a profit on them @$1800. (The shorts are willing to pay a premium below the peg because they believe their short position will be profitable, let them do it in a way that attracts customers for their shorts.)
If Bank A is new and or it risky it generally needs to offer me more interest for my deposit than a safe established bank. If it didn't there would be low demand, looking at the green side of our order book that is BitAssets current predicament imo. The BTSX virtual vault is new and risky & needs rewards to attract deposits and luckily competition from shorts is capable of producing a pot of funds that can offer the incentive needed in a self regulating way where it's not going to over-stimulate BitAsset demand in excess of shorting demand.
I like it personally, though as long as there was some form of self regulating method for maximising the order book by taking fees from those on the other side willing to pay a premium at 1-1 I'm happy.