I'm observing with pretty curiosity the wave of new challenger banks in UK (Staring, Mondo, Monese, Secco,...). I ask my self "Why big banks didn't start to build from scratch a new full stack bank". Notice, I mean to make a new bank really without add new abstact IT architecture layer on old legacy core banking system but create it from scratch (like starling). The problem of challengers is the trust (the majority of people don't love leave money in strange brand). I'm strongly convinced that a bank like HCBC or Barklays built with new modern technologies (REST, API Native, javascript, NOSQL, Spark,......) could be disruptive in terms of new services performed in real time (i.e. if new document is generated by sustem put it on my dropbox, native multicurrency). Basically my idea is the creation of an hybrid between challenger and big bank: a big bank bring the brand and trust of customers, a challenger bring innovation, tech and no legacy people. I see many advanteges (i.e. IT cost for customers drammactly decrease, new services could be offered to customers) apart the excess staff...