The short answer is "all of them"
I think the thing that folks miss about "disruptive technology" is that it literally disrupts the existing model of business. Thus even though "mobile payments" is considered "disruptive" - if you can come up with a solution that is better and serves potential customer needs better, you can disrupt the disruption.
And example of this occurred with HTTP/HTML In the late 80s early 1990s there were Prodigy, CompuServe and AoL that had online systems that allowed you to send mail and interact on BBSes.
Microsoft and IBM both were developing competing solutions to be rolled out in the 1993-1994 time frame when along came HTML from the physics lab CERN and completely disrupted the efforts of Microsoft and IBM (which was rumoured to be buying Prodigy)
The disruption was so complete that Windows 95 came out without a browser or an online mechanism because what Microsoft had been building was not compatible with HTML and Microsoft had to go out and license their first browser from a 3rd party when their attempt to buy a company was beaten out by AOL
So disrupting disruption is possible. Which means to some extent the question is poorly formed. No disruption is ever "saturated" that's the nature of disruption.
I also have a question about the very nature of your question. Periodically we see these types of questions "what part of Industry X is ripe for innovation" come through FD.
To me this seems like a flag saying
Hi! I want to innovate successfully in some market but I don't have any really good ideas or don't know any good ideas to invest in
Seems to me that's a formula for making a small fortune... out of a large one. Innovation, particularly disruptive innovation, invariably comes from either
Those are things you really cannot get from asking a question in an online forum. They are things that require creativity, perseverance, and luck
Very short answer: a form of intrapreneurship; i.e. spin out and buy a majority ownership (small valuation and large percentage) in a cost center in a fin that is a critical function but not a core competence or money-maker. Sign a long term service agreement with the fin spinning it out and leave it with a minority interest in a sub. Then convert the business to provide it to 3rd party customers and improve the economics of the business. Eventually you would capture market share, better control pricing, optimize your plant(s) and roll-up subs into one class of shares in an industry classification that commands higher private and public valuation multiples than the fin; i.e. unlocking locked value. Be sure you are an expert in the service space of the spin-out.Obviously there is more to this.