Hello Jon and thank you for the proposal,
I took a look at the Mossi Wikipedia, and indeed it seems that there is a good activity there, ans also the quality of many existing articles is really good. However, there are some points that I think need to be taken into consideration before moving forward:
1- many articles (even the bigger ones) do not have a single reference, and come of them are messy with just big chunks of text or very short (example: Busa, Guure). If these editors will be the future administrators, I think that they really need to be trained before. What do you think?
This is normal for new and emerging Wikipedia editions, and I am very skeptical of judging a new Wikipedia by the standards of well-established Wikipedias that have existed for decades. Of course, it is good to encourage best practices from the beginning, but I feel this is something each community must decide for themselves, if that makes sense.
2- the home page is fully written in English. This probably needs to be fixed before approval?
Ideally, yes, but I don't consider that a blocker for approval. Their current main page is just a "bare-bones" entry for contributors, and I expect they will replace it with a more proper main page once it is created.
3- the infoboxes bring information from Wikidata, but this is problematic because (a) they are very big with not always relevant information, and (b) none of the items is translated and all of them are in English. This is also something the editors need probably to look into?
This edition (and many others) use a standardized infobox template called "Databox" which fetches things from Wikidata automatically. If there are labels in Mossi for the items mentioned in the infoboxes, the Mossi label will be used (well, at least in the created wiki – I haven't checked whether that's implemented for Incubator test wikis, but I think it is). (Side note: I have been thinking of making a gadget for the Norwegian Bokmål Wikipedia that makes it easy to add Norwegian labels directly from the infobox without having to visit Wikipedia. Such a gadget could also be useful for the Incubator.)
The Databox template can indeed be a bit big and unwieldy at times, but I think it's still better than nothing. It is also meant to be easy to set up and use without having knowledge about the Lua code that is necessary to make more sophisticated Wikidata templates.