As libraries become more available or the nature of our clients change, we can switch. We certainly look forward to having the smaller keys that ECC will give us.
We are aware of tweet-nacl, but we are trying to avoid the number of external JS libraries we would need. This is why the Teams web app is limited to browsers that most fully support WebCrypto.(Of course our own browser extension for Desktop 1Password runs in more browsers as it does not rely on any crypto itself.)
I admit it is kind of weird using GCM where a stream cipher would be faster, lighter, cheaper. And so we definitely are looking forward to moving to something like that for our transport layer encryption. There aren't any security problems with our current ciphersuites, but we should be able to improve performance by using things like what you recommend.
1. Limited algorithms. This is what has use using GCM instead of a stream cipher for our transport layer. 2. It allows developers to shoot themselves in the foot by not enforcing best practices. 3. It encourages crypto delivered over the web.
If (3) is your concern, then it doesn't matter how good, modern, up to date, the methods are. This objection applies to tweet-nacl just as well.
If (1) is your concern, keep in mind that there is nothing wrong with the algorithms and modes we are using. Sure we had to forego some slicker alternatives, but this is a performance hit.
If (2) is your concern then what is true about WebCrypto is true of almost every crypto library out there. Whether we use libcrypto, CommonCrypto, MS CAPI, etc, we have just as great a chance of "using it wrong" as we do with WebCrypto. WebCrypto isn't worse than most of the alternatives, it is just new enough that we all hoped it would be better than the alternatives in this regard.
So given these three general concerns with WebCrypto, you need to make a judgement about how these play out when evaluating 1Password for Teams.
