I would suggest to include also www.OpenSeaMap.org
In OpenSeaMap, Wikipedia is already integrated: http://map.openseamap.org/map/?zoom=11&lat=36.0238&lon=-5.46748&...
OpenSeaMap does not look ready for production. I get tons of broken tiles there. We'd have to host the tiles ourselves. To be honest I do not think that it is a good idea to start hosting tons of different tilesets, just because they are there. I'd start of with the bare minimum and focus on what is important for encyclopedic applications. The location of shipping lanes and individual marker buoys (or whatever those are called) does not strike me as information that i terribly relevant for our average reader.
That being said, we should definitely have this discussion once we have an initial setup deployed. THEN we can gather feedback from the users and think about broadening our map offers.
Daniel