I do like the business model of swapping BTC for tBTC.
Me and most others here don't. tBTC are intended for testing and are meant to be passed around for free, such that they don't develop monetary value.
I do feel there is a need especially with large scale testing of apps.
Why can't you just use smaller fractions of BTC to test your apps? E.g. instead of sending 0.1tBTC from a test user to another, you just send 0.0001tBTC.
Also, there is
regtest, which is probably the best idea for app testing.