Form follows function, structure needs to support the business plan/resources. Operating leaner, while necessitating structural trade-offs, doesn't have to also mean losing'DNA sequences' if leaders focus on identifying desired capability and value; map this across current structure/capabilities/resources; determine how/where to best develop said value and develop clear metrics to track progress/flag deviations & make adjustments as the company establishes its footing over the next 6-18 months. Structure can take many forms - with intention (and some investment), DNA and culture can remain (mostly) congruent.
I would also venture to guess there are, beyond structural solutions, effective ways to support desired value creation (like what a separate quality organization offers) through management, process and cultural development as well. (Equifinality = there are many paths to the same goal -- http://en.wikipedia.org/wiki/Equifinality . Being a 'leaner' organization, there are likely important trade offs to be considered, the negative effects of which can be minimized with good planning/intentional design, leadership awareness/consistency and well-targeted management/employee engagement & development.
Culture is best defined as, "how we do things around here", is rooted in the assumptions, beliefs and values (values = what's most important) of the collective and is mostly influenced by leadership + customer environments. You have high-talent/experienced leaders in place who are already in sync with customers/markets - the path to 'striking a balance carving out a new identity while retaining DNA' rests in engaging leaders (and others) in the right dialogues/assessments (grounded in systems thinking) and guiding a process for them to develop the right systemic capabilities/awareness, establish desired assumptions/beliefs and infuse/support desired values throughout the organization.