Consensus building is not agile, takes a lot of time and generates lots of garbage and heartbreak. I am much more confortable with the use of "Consent" from Sociocracy/Holacracy, are you familiar with them?
On Holacracy, for example, the whole Governance process is agile, based on Circles and Roles that have a clear purpose, and evolve accordind to the organization's perception of its surrounding reality.
The process to evolve Governance is through Consent. It all starts when any member of the Circle brings a Tension during a circle governance meeting. He alone feels that Tension, and thus he will be responsible for creating a proposal. This proposal is then presented and clarified. Then everyone has the chance to bring up rational, clear Objections, but not everything is a valid objection, for instance, not liking the proposal is not a valid objection. THe only valid objections are those that prove that poposal will move the circle back or will cause harm too serious to even try.
The role of a Facilitator is crucial during these meetings to help sort through the objections. But Holacracy also has its flaws, for example, it doesn't take into account the org's Tribal Space, so personal relationships and caring are not part of their practices, then it starts to become too mechanical, looks like you are a part of a software.
Then there is a brazillian company called TargetTeal (inspired on Lalloux's Reinventing Organizations) that created an adaptation based on Holacracy, called Organic Organization , or O2 for short. It's basically a simplified, open source, version of Holacracy, that looks much less like you are part of a running piece of software, and it actually includes a Caring meeting mode, where everyone leave their Roles behind and uses techniques based on Non-Violent Communication to actually sort out relationship issues, by using empathy and expressing in am authentic way.