I'm a developer. We have a non-technical BA writing our stories. There are a few stories coming down the pipeline that have a small business description. These stories require an unusually large amount of technical design and work. We do not want our non-technical BA writing up a bunch of technical detail. We also do not want a single story that consumes 3 sprints of effort.
Contrived example story
"As a user I need to identify our top paying clients so that I can send them a gift"
The technical design of this feature is complex. It's ~3 sprints of work. If we break it down then it will turn into a bunch of technical tasks.
Please note this is a contrived example. Roughly, the complexity of implementing this story involves writing complex analytical algorithms to aggregate the necessary data, writing several new API's to support the need, and calling into disparate legacy systems...in other words a bunch of technical this and that.
How can we resolve this kind of problem?