is it possible to build a coin which never goes below 1 usd but has the potential to increase to any number? if yes, there is a potential use case for a DAPP.
One way to get this characteristic might be a hybrid between a USD backed stable coin (USDM) and an algorithmic stablecoin, for example Djed/Shen (worth checking out if not already).
To stop something dropping below 1USD you would need to back each token with 1USD so it was fully redeemable. If the treasury was reinvested so that the value of the treasury increased over time the value of the token would always be greater than a dollar, and if each token issued had a fixed percentage of the treasury based on the total tokens in circulation it would increase slowly roughly in line with inflation of the fiat currency.
Combining the stable coin with an algorithmic reserve coin like Shen in a suitable ratio (e.g. 95% stable, 5% algorithmic reserve) might allow you to generate additional returns as you could get some exposure to the cryptocurrency.
However there is nothing to stop you doing this yourself, buy 95% USDM and 5% Shen and you are pretty close!
Are you sure that you have a use case there?
If the “half-stable” coin or whatever you wanna cool it can go to any value, it doesn’t help the people who buy at those arbitrary high values much that it can never go below 1 USD (or the equivalent in ADA or the equivalent in USDM or DJED). They can still lose an almost arbitrary amount of money from that deal.