I think this could be handled through advertising. Unfortunately, policies for advertising at SE are a bit murky.
I read somewhere that there are free advertising opportunities in the sidebar for open source projects - SO had users vote on it back in 2009 - but I don't see anything for GIS.SE. It sure seems to me SE needs to focus on getting an ad placement engine working. For example, it would make sense for an advertisement for this class to appear on an R related gis question. There should be feature in GIS.SE that would allow users to place ads there without going through a long drawn out voting process. I think the ads should appear along the side bar, not as large images, but unobtrusively - like they do in gmail.
I bet at least some of the VC's who've invested in SE are expecting tools for ad placement.
OK, I just found the link about community promotion ads. Still,
The goal is to help visitors find out about the cool stuff your
community is doing and help promote activities they find important.
And it’s all visible right there on the sidebar next to every
question, and the homepage.
IMO it doesn't need to be next to every question - only next to relevant questions. We need to have features that allow for targeted ads.