But one thing that would seem basic and absolutely necessary is BTC stablecoins. If I'm supposed to pay back a certain fiat amount every month, there's no other way than paying back through the smart contract, which means a Bitcoin-USD token. 

 I’ll ask @janusz about this today.

My guess is we probably need a soft fork to get to the full level of functionality you’re looking for. 

 It's not so much that I'm looking for it but that I don't see another way for BTC to keep its property of being trustless and be collateral at the same time. 

My bet in BTC is predicated on the assumption that this will eventually be solved, because other inferior projects have solved it. But it would seem not yet. 

 Or maybe one could say they’ve solved it but only on a mostly centralized and non-censorship-resistant blockchain. 

 I don't think having smart contracts is related to being centralized. 

 It shouldn’t be.