I've not heard anything about adding additional HMAC implementations, but that doesn't mean it isn't planned.

I agree--there must be a lot of apps with issues right now, some subtly buried.
Although the data is coming from a third party could you filter it through a simple web service that replaces nulls with zeros or some defined value that the app could be…

You may be able to restructure your data and avoid the problem all together. (hint1: DO NOT use large multidimensional arrays!

I'm still mentally having a hard time wrapping me head around the fact that they are exclusion annotations rather than inclusion annotations.