First of all: I'm sympathetic to a formal expansion of the scope of the performance team. It has been one of the most reliable teams during turbulent times for the the organization as a whole, and a tremendous help to the ops team. The team has gone above and beyond their responsibilities in their work, so it feels right to expand the charter of the team to cover the work it has been doing.
That said, I am a bit skeptical of the "availability" term and have been so independently of this proposal. The reasoning is two-fold: first, it feels like a lot of the work fits as awkwardly to availability as it does now to performance, e.g. the Thumbor work (work that needs to happen for a variety of reasons: availability, performance among them, but also security and product-focused features) or the MediaWiki URL routing work. Calling it "availability" feels like just listing another aspect of some of the great work that happens within that team, not unlike its performance aspect right now.
Second, this team's work on availability isn't cross-cutting right now and I wouldn't expect it to be given its current resourcing in headcount and skillset; the team hasn't worked on the availability of either other independent but critical infrastructure components (like e.g. RESTBase) nor it has dealt with availability plans at large (e.g. disaster recovery scenarios in case of partial or total failures of datacenters). Aaron's comment about the "uptime" KPI reflects on that as well.
My counter-proposal has been something along the lines of "core platform", but I realize that the term is both tainted by our past and also quite vague so it may not be the best of ideas :)