That means attackers could sell a lot of NBT when BTC price drops because they can transfer more BTC whth their NBT, and attackers will buy lots of NBT when BTC price go up with less BTC.
That is counterpart risk!
Stop this! Negotiate with exchange for just “display” buy wall BTC while actually we holding USD. Otherwise, cancel all NBT/USD pairs, I suggest.
When price of BTC goes down against NBT, BTC goes down against USD.
When BTC is US$400 NBT/BTC rate is 0.0025.
When BTC goes down to US$350 NBT/BTC rate will be ~0.0028
In both cases NBT/USD rate stays the same.
In your example halving the price of BTC would result in doubling the rate of BTC/NBT.
Maybe @Chronos misunderstood your question?
Edit, thanks Ben you triggered me. This is about a buyback fund. The issue is that you can’t hold a buyback fund in BTC or NBT. It has to be USD or a very stable commodity against USD outside cryptoworld. Maintaining such fund would create challenges in managing and regarding decentralisation. Keeping the fund on the exchange in US$ would create an exchange default or hacking risk.
Another option is to introduce another NuBits coin pegged to a relative stable currency like Euro or Yuan. The buyback funds can then be held in multiple wallets with multi-sig and would be relatively safe. Only risk remaining is changing EUR/USD or CNY/USD rates.
Disadvantage is that you wouldn’t be able to make the money work, so I think it would be hard to make a viable business model attractive to the stakeholders. Only option I can think of is reducing the buyback fund to 80% or maybe even 50% instead of 100%.