like binance is doing with tether - they are "printing" fake casino money to inflate price of BTC using USDT (80 billions currently) - if anybody decide to create crypto market exchange and create for example USDA token (just like USDT alternative with also "covered" 1:1 to USD dollar) and print every day few millions of USDA - and then buy BTC to inflate price to 1'000'000 USD/BTC.
There are facts you should know:
USDT is backed by promises: There is no 1 USDT == 1 USD in bank, and therefore all that preserves its value is to continue to make promises that there is a real dollar for each USDT, and therefore you should avoid it if you want a stablecoin outside the platform.
USDT is used within the exchanges and this is only a small percentage (less than 10%) of the
real Bitcoins.
I was shocked the day I came to the realisation that, no usdt or any of the stable coins we have out there, pegged with dollar as actually backed by a single dollar (perhaps just 10%) but that's insignificant and yet, they tend to play there game so we'll that people actually believed and keyed into the idea of using it. Even up to this moment and that's because, its actually delivered on most of its promises as per giving coins some stability no matter the market condition.
On the other hand with OP, it's possible to create own platform but, its nothing if it haven't got the liquidity and volatility to deliver on its promises. It would as we be tearmed scam and raise red flags.