The TXB chips look nice, but they're overkill for programmer or serial port, since those functions don't need the signal lines to be "bi-directional."
But you will need some kind of level translation. As you note, the FT230x is capable of running the IO side at 1.8V levels. Perhaps it's "big brother" (FT231x) would be usable as both serial interface AND for programming in "FTDI bit banged" mode?