WrapDB provides a simple way to download source dependencies automatically. Basically it takes an upstream release tarball, adds Meson build files to it if needed and publishes the result on the web. The work consists mostly of reviewing and merging submissions from the community. Creating your own is also fine. This is a fairly lightweight task, only requiring actions every now and then (submissions come less than once a week, typically).
CI fixer upper
For CI we use the free tiers of Travis and Appveyor. This works fairly well but it is very slow because our testing matrix is huge. Running the full test suite through AppVeyor takes about an hour. This slows us down a fair bit and in addition both CI providers have a nasty habit of breaking down fairly often. We also don't want to do priced tiers because they get ridiculously expensive for our usage pattern (as in, a few months of paid for macOS would cost more than a brand new Mac Mini).
We don't have any good ideas on how to make this better. If you do, let us know.
Large scale regression tester
Meson is being used by a fairly large number of projects. This makes fixing bugs and refactoring code challenging because there is the possibility of regressions. It would be nice if we could do something similar to Rust developers and rebuild all or a large fraction of projects using Meson with the trunk version every now and then.
XCode backend improvements
The XCode backend is currently a bit crappy. The main reason for this is that the XCode project file format is awful in many ways. The two main reasons being that it is completely undocumented and the fact that it is not really a file format as such, but more of a memory dump of XCode's internal data structures. But if you are the sort of person who enjoys a challenge of battling against windmills, this might be for you.
Meson build file rewriter
Integration with IDEs and the like is important and we want to provide tools for operations such as "add source file X to target Y" so everyone does not have to write their own implementations. There is actually code for this in trunk but it is quite limited and has bitrotted a fair bit. Resurrecting and making the code actually work would be very welcome.
This one also aims to improve the IDE integration features of Meson. As an example you can only get information about build targets one by one. This means that getting the information from a project that has thousands of targets takes forever. We really need a batch exporter so IDEs can grab all necessary project information in one go. There are probably a bunch of other things to improve as well.
Could these be done as part of gsoc/outreachy/other?
Possibly. Meson is not really an "entity" in the gsoc sense but we could potentially get something accepted under the Gnome umbrella. However anyone is welcome to submit patches, obviously, and several of the topics listed above are not nicely self-contained projects that would fit in the gsoc mold at all.