The usual workflow for my team looks something like this: features are planned by product management and then collectively broken down to business requirements. Then the developers start working separately through those requirements one by one until the next feature comes around.
One issue I noticed is since the stories are implemented in an incremental way the associated code tends to be slapped on the existing code. Initially it is easy to make sure the new code somehow fits with the old code. But over time portions of the codebase begin to diverge and the whole thing turns into patchwork.
I have been thinking an initial design story to put down method and test stubs, discuss the development strategy to follow etc. for the rest of the stories can help with this although I am not sure how exactly it would work.
Alternatively or alongside this I want to propose switching our code review system from a single peer review by a tech lead to a consensus system, but not sure how the alternative would look like as far as what everyone would review for, how much effort would go into it, what kind of standards we would follow or how I would go about proving it would bring value.